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Sturgeon's House

Contemporary Western Tank Rumble!


SH_MM

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34 minutes ago, SH_MM said:

 

Negative. The drawings from the declassified CIA report cannot be corrected in order to provide accurate information. Even applying both values measured by Gaijin shows that they do not match. Adding a third value - such as the well documented and proven thickness of the upper glacis plate - only shows more conflicts with the other values... and that remains the case even after fixing the wrong orientation of document in the scanner and fixing distortion using software.

 

 

And what exactly makes you think that the turret front of the M1 Abrams can withstand the XM774 APFSDS and that the armor value from the CIA document refers to the XM774 APFSDS? There is no source or reason for such claims. This seems to be rather your "feeling" than any logical claim.

 

First of all, the CIA document is very unspecific regarding the protection level - at what angle is the protection level achieved, what round is used as reference and why does it talk specifically about "one version of the M1 turret"? You seem to make assumptions regarding all these questions and then use these assumptions in the next step to claim that the M1 Abrams' turret could resist the XM774 APFSDS. I cannot agree with that, as you are ignoring a number of other facts and there is no basis for coming to your conclusion given the lack of supportive arguments.

 

In the previous and in the following paragraphs of the very same CIA document, US estimates for the performance of tungsten-carbide cored/tungsten alloy APFSDS rounds of Soviet origin are mentioned. It would be a very stupid way of displaying data - using values for WC/WA at all places but one - specifically given that the US was very aware of the higher efficiency of monobloc rounds against multi-layered targets since at least 1975/76 (more on that later).

 

The statement regarding "one version of the M1 turret" is also interesting, given that the work on the M1E1 already had started at the time! The CIA - in a different document - attributed the M1A1 Abrams tank with 380 mm steel-equivalent protection against an unspecified APFSDS round...

 

 

There was no requirement for protection against the XM774 APFSDS and the 1976 ballistic tests conducted on the XM1 prototypes and the Leopard 2AV did not involve any XM774 APFSDS rounds. We know that according to the SAIFV vulnerability in 1978 the XM1 armor was not able to stop the XM774 APFSDS and that the performance of the XM774 round against BRL-1 (and at shorter ranges possibly also against BRL-2) - which was seen as comparable to the frontal armor fo the XM774 - was considered satisfactory by the US Army also in 1978. In 1978 also the FSED prototypes were delivered, which were basically identical to the later series version. You state that the turret front was likely better protected and hence could survive hits from the XM774 APFSDS projectile, but the British assessements of the XM1's armor suggest that the difference was nowhere as large as you suggest; i.e. the different parts of the tank were designed to withstand from 400 meter different distance (800 m instead of 1,200 m).

 

The US Army also noted in the 1978 hearings on the smoothbore gun, that the XM774 likely performs better than the 38 mm two-piece tungsten round (DM13 APFSDS prototype) fired in the tri-parite gun trials of 1976; while the initial 1976 trials did not include Chobham armor targets like BRL-1 and BRL-2, this belief was based on the (poor) performance of similar US designs (i.e. XM579 and later XM735, which was adopted as new designation for the later XM579 prototypes) against such targets. In other words: if the XM1's turret fornt was able to provide protection equivalent to 400 mm of steel armor against the XM774 APFSDS round, then it would provide significantly more protection against XM579/XM735 and DM13... weird that they only specified protection against the 105 mm XM579 round at 800 meters then, when it should rather be 0 meters distance.

 

If the XM774 would be better against BRL-1 (XM1 equivalent armor) than the German 120 mm APFSDS with 38 mm tungsten alloy cores, then the armor would be immune against the XM579/XM735 rounds. The 105 mm version of the DM13 APFSDS (with an identical penetrator with 38 mm tungsten alloy cores) could penetrate 165 mm steel armor sloped at 60° at 800 meters distance - but German steel made to the TL 2350-001 specification. This steel was found to be considerable better than RHA manufactured to US specs during the 1976 tri-partite gun trials. So this round is already superior to the XM579E4 APFSDS. The Leopard 2AV was required to stop the 105 mm APFSDS round with 38 mm tungsten cores from 200 meters distance and the 120 mm version from 1,500 meters distance. If the XM1's turret survived hits from the XM774 at point blanc range (as you essentially claim), then it also would be immune to 120 and 125 mm APFSDS from point blanc range until the mid-1980s. This is clearly not the case based on the requirements, specifications and the development of the M1E1/M1IP tanks.

 

Also in 1978 the UK believed that a monobloc DU APFSDS capable of penetrating 445 mm of steel armor at 1,000 meters would be sufficient to defeat the frontal turret armor of the M1 Abrams at distances in excess of 4,000 meters.

 

_______________________________________

 

If anything the 400 mm figure is a reference to the protection against APFSDS rounds with WC/early WA cors or a reference to the M1E1 tank's specifications. It also could be a mix both at the same time.

1. I wasn't clear enough, I don't scale of plate thickness rather the outside dimensions, and by doing that I am able to get the proper plate thickness. I am surpriced you can't, but I have disagree with you blanked statement that you can't get any accurate information off the drawings. Sure its not blueprint quality, but for our purposes its much better than nothing and we are within a cm of accuracy.

 

2. First, even if the turret only provides protection against XM579 out to 25 degrees then due to the angle of the armor its going to be providing protection against XM774 just over a narrower cone, Read SAIFV again and look at the angular protection of the side armor against XM774. You don't need many degrees between XM579 and XM774. 

 

Here is the quote from NYT 23-03-1978:

"The XMl guns will fire a kinetic energy round that Army experts say travels at about a mile a second and can penetrate 15 inches of armor. But not, they add, the new armor.".

 

The same CIA report that states 400-750 also states:

"Should the Soviets archive the same muzzle velocity in the RAPIRA-2 125mm smoothbore AT gun as they do with T-64/T-72 main gun, they will be able to penetrate 350mm og RHA at 2,100M. In other words, USAARMC is also increasingly concerned about KE warhead composition (WA, DU), and development of a hypervelocity antitank system which may become a threat to the M1 system, especially at shorter ranges."

So they don't think that the soviets are clearly over matching them yet but it is getting closer. And they are concerned about the soviets developing a DU round. This indicates, to me at least, that the Abrams has better protection than 350mm from the front turret.

 

We also know that the CIA discovers in the late 70ties that they had underestimated the capabilities of the T64/T72 and that the superiority of the Abrams they had estimated back in 1972 was not going to be realized. At the same time the Abrams gains in weight, in 1978 0.9 tons are added to the tank in form of ballistic protection finally pushing the tank to 60 tons, 2 tons over the original 58 requirement. Source: "Transportability in the defense department. By Zycher and Morton. 1992"

 

So we do actually have evidence that the Americans added to the armor protection before production commenced, and that in 1982 they where only worrying. 

 

I appreciate your time and information! Though trying to say that the CIA report is really just talking about the M1E1 I find really doubtful, given that the CE protection is only 750. My suspicion is that when they decided on the armor of the M1A1 their major concern was not KE weapons rather it was CE, you can read in one of their reports on the Russian tanks that they estimate that the Russians will soon develop a missile capable of overmatching 750mm steel. Thats why they add 200mm to the turret front to protect against CE.

 

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8 hours ago, STGN said:

1. I wasn't clear enough, I don't scale of plate thickness rather the outside dimensions, and by doing that I am able to get the proper plate thickness. I am surpriced you can't, but I have disagree with you blanked statement that you can't get any accurate information off the drawings. Sure its not blueprint quality, but for our purposes its much better than nothing and we are within a cm of accuracy.

 

This is impossible, because the relation between the plates is wrong and the outside dimensions won't change that, hence you cannot get the proper plate thickness.Based on the fact that you are apparently overlooking the fact that the drawings from the Special Armor Secuirty Classification Guide only serve the purpose to illustrate the armor layout and are not blue prints or scale drawings, you are introducing massive flaws to your measurements/model and thus I cannot consider them in any shape or form valid for further discussions.

 

We have five confirmed measurements for the Abrams hull armor:

  • the upper glacis plate behind the special armor module
  • the upper glacis plate over the special armor module
  • the lower glacis plate
  • the back plate
  • the distance from outer edge to welding seam

Regardless how you scale according to outside dimensions, the relationship between thickness of the different plates remains wrong. The upper glacis plate above the special armor module and behind the upper glacis plate special armor module are both aligned on the same slope, so changing the outside dimension of the whole array won't fix that. The UFP behind the special armor cavity should be twice as thick as the UFP covering the special armor cavity as confirmed by measured values on the actual tank - but that's not the case. It is just ca. 50% bigger.

 

Likewise the frontal hull plate with a LOS thickness of 31.75 mm should fit 3.27 times into the back plate, if angles are adjusted. It fits however 3.5 - 3.6 times into the backplate. The UFP above the crew compartment (with 38.1 mm line of sight thickness) fits three full times into the 4 inch backplate, which also should not be possible. Regardless what plate I use to calculate the distance to the weld line, it never matches the measured value.

 

 

The relations between the armor plates are wrong. Scaling the whole image according to outside dimensions won't fix that. Given the inaccuracies between the plate thicknesses, assuming that any other dimensions and relations are accurate is silly.

 

8 hours ago, STGN said:

2. First, even if the turret only provides protection against XM579 out to 25 degrees then due to the angle of the armor its going to be providing protection against XM774 just over a narrower cone, Read SAIFV again and look at the angular protection of the side armor against XM774. You don't need many degrees between XM579 and XM774. 

 

This is wrong for two reasons:

 

  • First of all, you ignore the differences in angle. Changing the angle of impact from 25° to 20° increases the line-of-sight thickness by 24%. Changing the impact angle from 90° (i.e. hitting perpendicular to the turret armor module) to 65° (hitting directly from the front) increases line-of-sight thickness by only 10%.
  • Last but not least, until the late 1980s, APFSDS projectiles performed worse against steeply sloped armor, specifically against spaced armor arrays. So even if the frontal armor was 24% thicker, it wouldn't be guaranteed to provide the same amount of protection as the side armor against the XM774 APFSDS/simulated 115 mm APFSDS (DU).

If anything your argument has backfired and only shows that jugding by the reduction of the impact angle, until which the side armor can resist the XM774 APFSDS, the turret armor cannot withstand even a fr

 

9 hours ago, STGN said:

The XMl guns will fire a kinetic energy round that Army experts say travels at about a mile a second and can penetrate 15 inches of armor. But not, they add, the new armor

 

This is again an example of you making an assumption, then making another assumption all in order to support your first unproven assumption. There is no statement that the new APFSDS round that can penetrate 15 inches of "armor" is the XM774 APFSDS. Aside of the fact that newspaper articles written by civilian journalists have a tendency to be inaccurate and full of sensationalism. Neither the XM735 nor the XM774 achieve a muzzle velocity of a mile per second.

 

The 15 inches of penetration is a generic figure and can mean anything given the wide range of unknown factors. Even the XM579E4 and XM735 can achieve 15 inches of penetration against steel armor under the right conditions. Furthermore the 15 inches figure appears to be a rough value given by a US official to the press, rather than an accurate value. "[T]he new armor" can as well be a generic statement in regards to Chobham or composite armor, rather than being a direct reference to the actual armor of the XM1 tank. The NYT article throws in several references to the - then in development - M1E1 tank.

 

The article also claims that the 105 mm gun with the then availablle ammunition would be sufficient to defeat Soviet tanks (it was not according to declassified CIA reports), the 120 mm gun would be overkill (it was not). It is not a reliable source, at least nowhere as reliable as the sources I have provided.

 

9 hours ago, STGN said:

So they don't think that the soviets are clearly over matching them yet but it is getting closer

 

Yet this is nowhere directly stated.

 

9 hours ago, STGN said:

We also know that the CIA discovers in the late 70ties that they had underestimated the capabilities of the T64/T72 and that the superiority of the Abrams they had estimated back in 1972 was not going to be realized.

 

They hadn't stopped underestimating the Soviets by the time the CIA document was written.

 

9 hours ago, STGN said:

At the same time the Abrams gains in weight, in 1978 0.9 tons are added to the tank in form of ballistic protection finally pushing the tank to 60 tons, 2 tons over the original 58 requirement. Source: "Transportability in the defense department. By Zycher and Morton. 1992"

 

So we do actually have evidence that the Americans added to the armor protection before production commenced, and that in 1982 they where only worrying. 

 

Yes, the armor was added to the FSED prototypes manufactured in 1978, which according to R. P. Hunnicutt served a reduction of weak spots rather than increasing the protection level against newer threats.

nm8ZFrR.png

The improvements to protection included a new special armor gun shield compared to the previous one (made of cast steel only) and an increase in special armor module height in order to expose less roof area to the enemy.

 

______________________________________

 

Your whole approach to the topic seems to be questionable. From my perspective you seem to have started with the opinion "the (X)M1 Abrams can survive the (X)M774 APFSDS" and then search for any sources that are vague enough that you can add your own interpretation.

 

"One version of the Abrams turret has protection equivalent to 400 mm RHA vs APFSDS rounds? That must be a reference (X)M1 and the (X)M774 APFSDS! An unspecified APFSDS round can penetrate 15 inches of armor at unspecified range and unspecified angle? That has to be a proof that the (X)M1 Abrams is protected agains that!" - yet we have much more detailed and clearer sources specifically stating that the Abrams in 1978 - the same year most of your "sources" (which are sources, just not for your claims) are from - was not protected agains the XM774 APFSDS round.

 

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13 minutes ago, SH_MM said:

That also explains why the UK believed the M1 Abrams could be defeated using 125 mm monobloc APFSDS rounds at distances greater than 4,000 meters!

problem with UK round was yaw, thats why it's penetrated BRL-2 "randomly" 

 

there was also some tests with 

 

BRL1 at 60 deg

XM774 26 diam - 7,5km 50% of pen

BRL1 60 deg FRG  120 tungsten - 10km

BRL 2 60 deg same - 2km

 

tODs1qswFV4.jpg

 

and some DU tests etc...

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10 hours ago, STGN said:

1. I wasn't clear enough, I don't scale of plate thickness rather the outside dimensions, and by doing that I am able to get the proper plate thickness. I am surpriced you can't, but I have disagree with you blanked statement that you can't get any accurate information off the drawings. Sure its not blueprint quality, but for our purposes its much better than nothing and we are within a cm of accuracy.

 

Sorry to jump into the discussion but this is outright silly. It's based on the believe that the schematics are perfectly correct in details they are not supposed to represent accurately. Anyway the general rule is that the only valid value from any drawing is the one with an explicit dimension - and that applies twice as much for any drawing from the old times when 2D was not yet simply generated from 3D by software. 

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40 minutes ago, Wiedzmin said:

BRL1 60 deg FRG  120 tungsten - 10km

 

This is the 38 mm core (DM13 prototype) or the 32 mm core (DM23 prototype) APFSDS? The previous document stated the inability of the 120 mm FRG tungsten round (38 mm core, I assume) to defeat BRL-1 at ranges greater than 2,000 meters.

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3 minutes ago, SH_MM said:

 

This is the 38 mm core (DM13 prototype) or the 32 mm core (DM23 prototype) APFSDS? The previous document stated the inability of the 120 mm FRG tungsten round (38 mm core, I assume) to defeat BRL-1 at ranges greater than 2,000 meters.

there is no any details, only that at some point brits used XL22E1, C24 and C81/31 APFSDS and germans used some "DU" round made from US Stabaloy, proto-XM827 maybe?

 

maybe difference is angles, maybe they really used some protoDM23 later, i don't know, now when archives is closed mostly we need some time to wait until it will open again but... , or maybe somebody have some additional info? 

 

@skylancer-3441 maybe you have something ?

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1 hour ago, Beer said:

Anyway the general rule is that the only valid value from any drawing is the one with an explicit dimension

Sometimes, not even that. Once I tried to create a 3d model of a T-55, based on technical drawings by UVZ, and they are not even close to the real thing when I compared the model to actual photos. 

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1 minute ago, heretic88 said:

Sometimes, not even that. Once I tried to create a 3d model of a T-55, based on technical drawings by UVZ, and they are not even close to the real thing when I compared the model to actual photos. 

 

There may be many drawings circulating and non-insiders have very little idea which version of a drawing is the recent and correct one. Sometimes even insiders don't know what they actually produce (real life experience from different field of products). Measurement on the real thing is clear on the other hand. 

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1 hour ago, Wiedzmin said:

there is no any details, only that at some point brits used XL22E1, C24 and C81/31 APFSDS and germans used some "DU" round made from US Stabaloy, proto-XM827 maybe?

 

As per the hearings in front of the Congress' subcommittee, the growth potential rounds were based on the future ammunition planned for use in the UK and FRG, but manufactured with US-supplied DU staballoy monobloc penetrators. The German growth potential round was based on the projected successor of the 120 mm APFSDS with two-part 38 mm core (i.e. DM13 prototype) used in the 1976 trials. It was better than the XM827 (DM13 with DU monobloc penetrator replacing the two-part tungsten core).

 

The Swedish trials of Rheinmetall's 105 mm smoothbore gun already included a 32 mm core tungsten APFSDS that performed better than the 38 mm core APFSDS round. As the 38 mm core APFSDS is apparently just the penetator of the 120 mm DM13 APFSDS adopted to a 105 mm catridge, it seems likely that the DM23 prototype is the 32 mm core tungsten APFSDS and also the growth potential round.

 

lUirhVo.png

4IRNPMS.png

 

It seems that:

Round used in 1975 = DM13

Primary candidate = DM23

Growth potential round = DM23 with DU penetrator

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14 hours ago, SH_MM said:

 

This is impossible, because the relation between the plates is wrong and the outside dimensions won't change that, hence you cannot get the proper plate thickness.Based on the fact that you are apparently overlooking the fact that the drawings from the Special Armor Secuirty Classification Guide only serve the purpose to illustrate the armor layout and are not blue prints or scale drawings, you are introducing massive flaws to your measurements/model and thus I cannot consider them in any shape or form valid for further discussions.

 

We have five confirmed measurements for the Abrams hull armor:

  • the upper glacis plate behind the special armor module
  • the upper glacis plate over the special armor module
  • the lower glacis plate
  • the back plate
  • the distance from outer edge to welding seam

Regardless how you scale according to outside dimensions, the relationship between thickness of the different plates remains wrong. The upper glacis plate above the special armor module and behind the upper glacis plate special armor module are both aligned on the same slope, so changing the outside dimension of the whole array won't fix that. The UFP behind the special armor cavity should be twice as thick as the UFP covering the special armor cavity as confirmed by measured values on the actual tank - but that's not the case. It is just ca. 50% bigger.

 

Likewise the frontal hull plate with a LOS thickness of 31.75 mm should fit 3.27 times into the back plate, if angles are adjusted. It fits however 3.5 - 3.6 times into the backplate. The UFP above the crew compartment (with 38.1 mm line of sight thickness) fits three full times into the 4 inch backplate, which also should not be possible. Regardless what plate I use to calculate the distance to the weld line, it never matches the measured value.

 

 

The relations between the armor plates are wrong. Scaling the whole image according to outside dimensions won't fix that. Given the inaccuracies between the plate thicknesses, assuming that any other dimensions and relations are accurate is silly.

 

 

This is wrong for two reasons:

 

  • First of all, you ignore the differences in angle. Changing the angle of impact from 25° to 20° increases the line-of-sight thickness by 24%. Changing the impact angle from 90° (i.e. hitting perpendicular to the turret armor module) to 65° (hitting directly from the front) increases line-of-sight thickness by only 10%.
  • Last but not least, until the late 1980s, APFSDS projectiles performed worse against steeply sloped armor, specifically against spaced armor arrays. So even if the frontal armor was 24% thicker, it wouldn't be guaranteed to provide the same amount of protection as the side armor against the XM774 APFSDS/simulated 115 mm APFSDS (DU).

If anything your argument has backfired and only shows that jugding by the reduction of the impact angle, until which the side armor can resist the XM774 APFSDS, the turret armor cannot withstand even a fr

 

 

This is again an example of you making an assumption, then making another assumption all in order to support your first unproven assumption. There is no statement that the new APFSDS round that can penetrate 15 inches of "armor" is the XM774 APFSDS. Aside of the fact that newspaper articles written by civilian journalists have a tendency to be inaccurate and full of sensationalism. Neither the XM735 nor the XM774 achieve a muzzle velocity of a mile per second.

 

The 15 inches of penetration is a generic figure and can mean anything given the wide range of unknown factors. Even the XM579E4 and XM735 can achieve 15 inches of penetration against steel armor under the right conditions. Furthermore the 15 inches figure appears to be a rough value given by a US official to the press, rather than an accurate value. "[T]he new armor" can as well be a generic statement in regards to Chobham or composite armor, rather than being a direct reference to the actual armor of the XM1 tank. The NYT article throws in several references to the - then in development - M1E1 tank.

 

The article also claims that the 105 mm gun with the then availablle ammunition would be sufficient to defeat Soviet tanks (it was not according to declassified CIA reports), the 120 mm gun would be overkill (it was not). It is not a reliable source, at least nowhere as reliable as the sources I have provided.

 

 

Yet this is nowhere directly stated.

 

 

They hadn't stopped underestimating the Soviets by the time the CIA document was written.

 

 

Yes, the armor was added to the FSED prototypes manufactured in 1978, which according to R. P. Hunnicutt served a reduction of weak spots rather than increasing the protection level against newer threats.

nm8ZFrR.png

The improvements to protection included a new special armor gun shield compared to the previous one (made of cast steel only) and an increase in special armor module height in order to expose less roof area to the enemy.

 

______________________________________

 

Your whole approach to the topic seems to be questionable. From my perspective you seem to have started with the opinion "the (X)M1 Abrams can survive the (X)M774 APFSDS" and then search for any sources that are vague enough that you can add your own interpretation.

 

"One version of the Abrams turret has protection equivalent to 400 mm RHA vs APFSDS rounds? That must be a reference (X)M1 and the (X)M774 APFSDS! An unspecified APFSDS round can penetrate 15 inches of armor at unspecified range and unspecified angle? That has to be a proof that the (X)M1 Abrams is protected agains that!" - yet we have much more detailed and clearer sources specifically stating that the Abrams in 1978 - the same year most of your "sources" (which are sources, just not for your claims) are from - was not protected agains the XM774 APFSDS round.

 


I appreciate the good push back MM, make me go back and check my logic and arguments I haven't been doing this for years. In doing so I was able to recall how I made the measurements, I was conflating a few things but I will explain that later(another post).

 

First I have to repeat, because you apparently missed that I am not a hard core beliver in the Abrams having XM774 protection but I think its a possibility that the turret had it. If you go back to my first post I even say that I lean towards XM774 but I am not sure. However you have strawmaned me a bit talking about "my essential claim" etc.

 

1.Now you say it is wrong to consider the slope of the turret and you give great examples of why protection over a narrow front is possible. Remember US consider XM1 armor equivalent to 175mm(350/2) sloped at 60 degrees. Putting this on the both the right and left turret front we have to as you said multiply by a factor depending on the slope of the armor when shooting from the front. For the left side this factor is 1.22 and on the right side that is a factor 1.12

 

Left:

175 x 1.22 = 213.5 x 2: 427mm equivalent

Right:

175 x 1.12 = 196 x 2: 394mm equivalent

 

Your argument shows well how 400mm protection is a reasonable possibility head on, and for narrow cone of XM774 at 1000 meters.

 

2. No that is a quote, if you are allowed to make inferances and judgements based on referances why am I not? Also why are you trying to read my mind and make all sorts of negative judgements, what you achieve is just that you are arguing with your own projection of me. See you get to call 15" a generic figure and claim that it doesn't mean anything, yet somehow its exactly the same number as XM774 penetration.

 

3. But we do agree that 400mm is directly stated right? Again you get to make all sorts of excuses and explanations, but I am blinded by my need to have protection against XM774, right?

 

4. Now seeing as you love to ascribe all sorts of motivation to me, I can't help but notice that you seem to think that is somehow an argument, in this discussion, that the CIA keept underestimating Russian capabilities, you seem to have a rather negative attitude towards the US, could that cloud your view of the facts and lead you to draw wrong conclusions?

 

5. Cool argument bro, one thing though, that drawing and the proposals for turret redesign was made in 1976 not 1978 read Hunnicutt again. The turret redesign was made prior to Chrysler being selected as the winner.

 

 

Conclusion:

Your approach seems very negative and so overconfident you don't even notice that you prove yourself wrong, post erroneous information and freely attribute all sorts of negative assertions about my beliefs, you are calling me corrupt while you tell all sorts of stories, any info that doesn't go your way can be thrown away. So get a grip.

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10 hours ago, STGN said:

First I have to repeat, because you apparently missed that I am not a hard core beliver in the Abrams having XM774 protection [...]

 

If you weren't, we wouldn't have this discussion anymore. The point that the XM774 managed to defeat the BRL-1 special armor target claimed to be equivalent to the XM1 Abrams in 1978 should have been sufficient. Frankly any of the other sources should have been sufficient to make you question your own claims regarding the M1 Abrams' ability to protect against the XM774 round. Instead you have come up with other vague sources full of leaps of faiths and questionable assumptions...

 

10 hours ago, STGN said:

Now you say it is wrong to consider the slope of the turret and you give great examples of why protection over a narrow front is possible. Remember US consider XM1 armor equivalent to 175mm(350/2) sloped at 60 degrees.

 

That is the third time that you have claimed the XM1 supposedly was considered to provide protection equivalent to 350 mm steel armor (along a 60° frontal arc) and the third time you have failed to provide any source backing this claim up. Where is your source for this?

 

I've seen the 350 mm value four times, not once this can be considered a valid support for your claims:

  • S. Zaloga stated in his earlier books that the frontal armor of the M1 Abrams was equivalent to 350 mm steel armor. He did not specify an angle and has since started using Soviet estimates, showing that he apparently didn't have much faith in this value.
  • The Armor/Anti-Armor article published in the US infantrymen's magazine had a table in which the M1 Abrams front armor (again not frontal arc) was attributed with 350 mm steel-equivalent protection. The same table however claims the M60A1's frontal armor provides 325 mm protection vs KE rounds, which not only is inaccurate, but also shows us that this table isn't focused on a 60° protected frontal arc.
  • Jake Collins' now defunt wargaming reference collection of armor and penetration values, which unfortunately has been copied to dozens of web forums and still is used by ill-informed people, contained a value from Paul Lakowski attributing the M1 Abrams with 400 mm steel-equivalent protection based on a claimed 350 mm steel-equivalent protection along the frontal arc (which itself is a reference to Zaloga's original book). Paul L.'s old estimates have proven to be of extremely poor quality and he has since stated that his old estimates shouldn't be used due to inaccuracies
  • The 1982 (!) CIA document  "Proposal for interagency intelligence memorandum on Soviet armor program" contains a paragraph that the CIA assumes that in the future a Soviet 125 mm APFSDS round will be capable of penetrating 350 mm steel armor at 2,100 meters range. There is no statement that the M1 Abrams would be able to resist such a round along the frontal arc, instead it is clearly stated that the M1 Abrams' development was started under the assumption the Soviet 115 mm APFSDS rounds could penetrate 147 mm of steel armor sloped at 60° at a distance of 1,000 meters.

I have provided you with four (!) sources of higher quality  stating that the protected frontal protection of the M1 Abrams is focused on only a 50° arc, you have ignored that.

 

10 hours ago, STGN said:

Left:

175 x 1.22 = 213.5 x 2: 427mm equivalent

Right:

175 x 1.12 = 196 x 2: 394mm equivalent

 

Your argument shows well how 400mm protection is a reasonable possibility head on, and for narrow cone of XM774 at 1000 meters.

 

What you still massively fail to understand - aside of using an arbitrarly protection level of 350 mm along a 60° arc without having a source for it - is that RHA equivalent protection is not independent form the ammunition used. The 320-340 mm steel equivalent protection along a 50° arc (British assessment) or the 350 mm steel equivalent protection along a 60° arc (that you apparently pulled out of hot air) are achieved against the types of ammunition used to test the armor protection of the XM1 Abrams.

The XM579E4 APFSDS failed at defeating the XM1's armor at 1,000 meters distance, because it consisted of a high density early WHA alloy in a steel sheath. The penetrator core was very brittle and even simple spaced armor significantly affects its penetration ability. The XM774 was a monobloc DU penetrator, which is why it could defeat the XM1-equivalent BRL-1 armor target at ranges in excess of 4,000 meters (!) despite offering only 20 mm @ 60° more penetration.

 

Even with 394 to 427 mm steel equivalent protection against the XM579E4 and XM735 APFSDS rounds, the XM1 Abrams would not be protected against the XM774 APFSDS round. The same applies to the Leopard 2AV, which could stop the 105 mm K38 APFSDS round at 200 meters distance, yet was vulnerable to the monobloc 105 mm M111 Hetz APFSDS from distances as great as 2,000 meters.

 

Quote

Your argument shows well how 400mm protection is a reasonable possibility head on, and for narrow cone of XM774 at 1000 meters.

 

Aside of the fact that it literally doesn't. Only after you apply your unproven, unsupported protection values that stand in direct conflict with proven, supported values, it becomes possible. I certianly wouldn't call that "reasonable".

 

10 hours ago, STGN said:

See you get to call 15" a generic figure and claim that it doesn't mean anything, yet somehow its exactly the same number as XM774 penetration.

 

Because it is a generic figure. It also is the exact same number as the XM579E4 and XM735 penetration, if you use a shorter distance to the target or change the angle of slope.

 

10 hours ago, STGN said:

3. But we do agree that 400mm is directly stated right?

 

For "one version of the M1 turret armor" in a document that specifically calls about the possible need for improved protection and is from mid-1982, when the M1IP and M1A1 already existed as prototypes.

 

10 hours ago, STGN said:

I can't help but notice that you seem to think that is somehow an argument, in this discussion, that the CIA keept underestimating Russian capabilities, you seem to have a rather negative attitude towards the US, could that cloud your view of the facts and lead you to draw wrong conclusions?

 

The CIA has underestimated the Soviet armor and penetration capabilities. That is a fact. The whole NATO did until the mid-1980s and that is absolutely relevant to the topic, as the armor of the M1 Abrams, Leopard 2 and also the Challenger 1 was designed to stop rounds that fell well below the Soviet capabilities. The protection requirement for the M1 Abrams was to stop the XM579E4 APFSDS round, as the US Army believed that to be well ahead of contemporary Soviet 115 mm APFSDS projectiles. This is a confirmed fact and not for debate. Meanwhile we have no source and no indication that the XM774 was ever used to test the armor protection of the M1 Abrams. We have however a US General telling congress that the BRL-1 special armor target provided the same amount of protection as the XM1's armor and we have declassified documents proving that the XM774 could defeat the same target in excess of 4,000 meters.

 

I do not have a negative attitude towards the US. Check this topic and read the older discussions; I have argued the same way against people attributing the Challenger 1, Leclerc, Leopard 2 and other tanks with way too much protection without providing any sort of relevant sources.

 

What I am doing - and you honestly also should start, if you actually had an interest in finding the truth - is the following:

  • I assess the competency of a source. A declassified document written for the staff of the FVRDE, the BRL or a meeting of high-ranking US Army members will contain more specific and more accurate information than a newspaper article written for Bob, Bill and Karen. Likewise Steven Zaloga's books have less competency as a source than R. P. Hunnicutts, just like Lobitz's books are less competent sources than Spielberger's.
  • When there is a conflict between different sources, I will pick the one with the highest competency rather than choosing the one that best fits my opinion/my ideal believe.
  • If a source is vague, I will I look at all possible interpretations for it, rather than chosing the one that best fits my opinion. I will look at the semantics and at other sources with similar or higher competency - if there is a contradiction or not.
  • If a source is vague, I will not use it to base my whole argument on it.

I've always considered myself as a younger member of the community, but the high influx of kids playing WoT, War Thunder and AW might have shifted that. So let me use this phrase: Back in my day, we learned this at school and university.

 

You on the other hand are an Abrams fanboy who doesn't bother to consider alternative interpretations, and considers newspapers more relevant than declassified documents as long as it fits your opinion.

 

If a CIA report says "one version of the Abrams turret", a fanboy's knee-jerk reaction is: "This means that the XM774 cannot penetrate the turret". Meanwhile my first question is: Why did they write "one version of"? How does this fit along with the other sources? What is the context of this statement?

The CIA document is dated 1982 and is specifically focused on possible improved anti-armor systems from the Soviet Union. What sense would it make to refer to the original Abrams in this context, when the improved M1IP/M1E1 already exist and would hence invalidate the need to discuss possible armor upgrades?

 

Using your logic, we could use old newspaper articles, Wikipedia and Zaloga's old books to argue that Chobham armor consists of ceramic tiles in a special honeycomb matrix structure... and this argument would be valid, because the fact that we have declassified documents saying otherwise is irrelevant.

 

10 hours ago, STGN said:

Cool argument bro, one thing though, that drawing and the proposals for turret redesign was made in 1976 not 1978 read Hunnicutt again. The turret redesign was made prior to Chrysler being selected as the winner

 

Did you read what I wrote? The FSED prototypes were manufactured in 1978, the first on was handed over to the US Army in February 1978. One of the FSED prototypes was used for final ballistic testing in 1979.


We also know that the pre-FSEP Chrysler prototype had a weight of 58 tons, i.e. already was at the weight limit. As it is impossible that the FSED remained at the same weight as the earlier prototype, since it only added parts and increased armor coverage, Zycher and Morton have to refer to the FSED prototypes. They also stated that the design (with the 58 tons weight) was finalized in 1975, yet the FSED design was per R. P. Hunnicutt made in 1976. In other words: you are mistaken.

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On 9/19/2020 at 12:17 PM, SH_MM said:

 

If you weren't, we wouldn't have this discussion anymore. The point that the XM774 managed to defeat the BRL-1 special armor target claimed to be equivalent to the XM1 Abrams in 1978 should have been sufficient. Frankly any of the other sources should have been sufficient to make you question your own claims regarding the M1 Abrams' ability to protect against the XM774 round. Instead you have come up with other vague sources full of leaps of faiths and questionable assumptions...

 

 

That is the third time that you have claimed the XM1 supposedly was considered to provide protection equivalent to 350 mm steel armor (along a 60° frontal arc) and the third time you have failed to provide any source backing this claim up. Where is your source for this?

 

I've seen the 350 mm value four times, not once this can be considered a valid support for your claims:

  • S. Zaloga stated in his earlier books that the frontal armor of the M1 Abrams was equivalent to 350 mm steel armor. He did not specify an angle and has since started using Soviet estimates, showing that he apparently didn't have much faith in this value.
  • The Armor/Anti-Armor article published in the US infantrymen's magazine had a table in which the M1 Abrams front armor (again not frontal arc) was attributed with 350 mm steel-equivalent protection. The same table however claims the M60A1's frontal armor provides 325 mm protection vs KE rounds, which not only is inaccurate, but also shows us that this table isn't focused on a 60° protected frontal arc.
  • Jake Collins' now defunt wargaming reference collection of armor and penetration values, which unfortunately has been copied to dozens of web forums and still is used by ill-informed people, contained a value from Paul Lakowski attributing the M1 Abrams with 400 mm steel-equivalent protection based on a claimed 350 mm steel-equivalent protection along the frontal arc (which itself is a reference to Zaloga's original book). Paul L.'s old estimates have proven to be of extremely poor quality and he has since stated that his old estimates shouldn't be used due to inaccuracies
  • The 1982 (!) CIA document  "Proposal for interagency intelligence memorandum on Soviet armor program" contains a paragraph that the CIA assumes that in the future a Soviet 125 mm APFSDS round will be capable of penetrating 350 mm steel armor at 2,100 meters range. There is no statement that the M1 Abrams would be able to resist such a round along the frontal arc, instead it is clearly stated that the M1 Abrams' development was started under the assumption the Soviet 115 mm APFSDS rounds could penetrate 147 mm of steel armor sloped at 60° at a distance of 1,000 meters.

I have provided you with four (!) sources of higher quality  stating that the protected frontal protection of the M1 Abrams is focused on only a 50° arc, you have ignored that.

 

 

What you still massively fail to understand - aside of using an arbitrarly protection level of 350 mm along a 60° arc without having a source for it - is that RHA equivalent protection is not independent form the ammunition used. The 320-340 mm steel equivalent protection along a 50° arc (British assessment) or the 350 mm steel equivalent protection along a 60° arc (that you apparently pulled out of hot air) are achieved against the types of ammunition used to test the armor protection of the XM1 Abrams.

The XM579E4 APFSDS failed at defeating the XM1's armor at 1,000 meters distance, because it consisted of a high density early WHA alloy in a steel sheath. The penetrator core was very brittle and even simple spaced armor significantly affects its penetration ability. The XM774 was a monobloc DU penetrator, which is why it could defeat the XM1-equivalent BRL-1 armor target at ranges in excess of 4,000 meters (!) despite offering only 20 mm @ 60° more penetration.

 

Even with 394 to 427 mm steel equivalent protection against the XM579E4 and XM735 APFSDS rounds, the XM1 Abrams would not be protected against the XM774 APFSDS round. The same applies to the Leopard 2AV, which could stop the 105 mm K38 APFSDS round at 200 meters distance, yet was vulnerable to the monobloc 105 mm M111 Hetz APFSDS from distances as great as 2,000 meters.

 

 

Aside of the fact that it literally doesn't. Only after you apply your unproven, unsupported protection values that stand in direct conflict with proven, supported values, it becomes possible. I certianly wouldn't call that "reasonable".

 

 

Because it is a generic figure. It also is the exact same number as the XM579E4 and XM735 penetration, if you use a shorter distance to the target or change the angle of slope.

 

 

For "one version of the M1 turret armor" in a document that specifically calls about the possible need for improved protection and is from mid-1982, when the M1IP and M1A1 already existed as prototypes.

 

 

The CIA has underestimated the Soviet armor and penetration capabilities. That is a fact. The whole NATO did until the mid-1980s and that is absolutely relevant to the topic, as the armor of the M1 Abrams, Leopard 2 and also the Challenger 1 was designed to stop rounds that fell well below the Soviet capabilities. The protection requirement for the M1 Abrams was to stop the XM579E4 APFSDS round, as the US Army believed that to be well ahead of contemporary Soviet 115 mm APFSDS projectiles. This is a confirmed fact and not for debate. Meanwhile we have no source and no indication that the XM774 was ever used to test the armor protection of the M1 Abrams. We have however a US General telling congress that the BRL-1 special armor target provided the same amount of protection as the XM1's armor and we have declassified documents proving that the XM774 could defeat the same target in excess of 4,000 meters.

 

I do not have a negative attitude towards the US. Check this topic and read the older discussions; I have argued the same way against people attributing the Challenger 1, Leclerc, Leopard 2 and other tanks with way too much protection without providing any sort of relevant sources.

 

What I am doing - and you honestly also should start, if you actually had an interest in finding the truth - is the following:

  • I assess the competency of a source. A declassified document written for the staff of the FVRDE, the BRL or a meeting of high-ranking US Army members will contain more specific and more accurate information than a newspaper article written for Bob, Bill and Karen. Likewise Steven Zaloga's books have less competency as a source than R. P. Hunnicutts, just like Lobitz's books are less competent sources than Spielberger's.
  • When there is a conflict between different sources, I will pick the one with the highest competency rather than choosing the one that best fits my opinion/my ideal believe.
  • If a source is vague, I will I look at all possible interpretations for it, rather than chosing the one that best fits my opinion. I will look at the semantics and at other sources with similar or higher competency - if there is a contradiction or not.
  • If a source is vague, I will not use it to base my whole argument on it.

I've always considered myself as a younger member of the community, but the high influx of kids playing WoT, War Thunder and AW might have shifted that. So let me use this phrase: Back in my day, we learned this at school and university.

 

You on the other hand are an Abrams fanboy who doesn't bother to consider alternative interpretations, and considers newspapers more relevant than declassified documents as long as it fits your opinion.

 

If a CIA report says "one version of the Abrams turret", a fanboy's knee-jerk reaction is: "This means that the XM774 cannot penetrate the turret". Meanwhile my first question is: Why did they write "one version of"? How does this fit along with the other sources? What is the context of this statement?

The CIA document is dated 1982 and is specifically focused on possible improved anti-armor systems from the Soviet Union. What sense would it make to refer to the original Abrams in this context, when the improved M1IP/M1E1 already exist and would hence invalidate the need to discuss possible armor upgrades?

 

Using your logic, we could use old newspaper articles, Wikipedia and Zaloga's old books to argue that Chobham armor consists of ceramic tiles in a special honeycomb matrix structure... and this argument would be valid, because the fact that we have declassified documents saying otherwise is irrelevant.

 

 

Did you read what I wrote? The FSED prototypes were manufactured in 1978, the first on was handed over to the US Army in February 1978. One of the FSED prototypes was used for final ballistic testing in 1979.


We also know that the pre-FSEP Chrysler prototype had a weight of 58 tons, i.e. already was at the weight limit. As it is impossible that the FSED remained at the same weight as the earlier prototype, since it only added parts and increased armor coverage, Zycher and Morton have to refer to the FSED prototypes. They also stated that the design (with the 58 tons weight) was finalized in 1975, yet the FSED design was per R. P. Hunnicutt made in 1976. In other words: you are mistaken.

1. No see you are trying to argue that it is imposible for the Americans to have changed their mind about what protections level even a little bit and you are just so arrogant and condecending that I love pokeing at you becasue your manners are so bad.

Lets start with the turret of the original M1 Abrams, was it designed under a weight requirement of 59 tons or 60 tons? It was designed in 1976 according to Hunnicutt and I even have a picture of a model of it from 1976:
Snzqjc.jpg
So the improved FSED turret was done under the 58,9 tons weight requirement. So the 0.9 tons ballistic protection increase was added later:

RdWrIU.jpg
It even says in Hunnicutt that it was weight REALLOCATION:
vh10CY.jpg

When the pilot tank rolls of the factory floor in 1978 its even called a 59 ton tank:
QiLeYi.jpg

So it does indicate that armor was actually added to the turret.

How about the armor that is actually in the turret, the main pillar of your argument is the claim that the XM-1 had the BRL-1 armor from the 1977 trial where XM774 was able to penetrate BRL-1 at 4000 meters. However apparently you haven't read your own source:

Because it is not true that the XM-1 had the specific BRL-1 armor from the 1977 fireing trials it even says so in your own source! Lets set the stage, the 1977 firing trials where done to help evaluate wheter the XM-1 should keep the 105mm or development should swith to 120mm. The BRL-1 was a hypothesised T-72 and BRL-2 was a armor that was better than the XM-1:
I0PBoo.jpg
And what was the difference between BRL-1 and BRL-2 again:
6xfMh9.jpg
Does that sound like BRL-1 was the NERA and didn't have much KE defence? So how similar was BRL-1 to the XM-1's armor, well according to MR. Stratton it is "roughly the same":
D8NzQ6.jpg
So BRL-1 was infact a "representation of T72" and "roughly the same" but not the same as what was on XM-1.
See this source talking about the 1977 firing trial,  makes it sound like a "show trial" designed by the US Army to sell the 105mm M1 and wait with the 120mm M1. What they are saying "See the XM774 is going to be able to knock out the T-72 at incredible ranges, going for the 120mm is unessesary", "Is that actually the T-72's armor?", "That is classified sir."

So we are left with a question if the BRL-1 was roughly the same how roughly are we talking? Allow me to introduce the Special Armor Infantry Fighting Vehicle(SAIFV) study. Because here we can get the numbers through the vulnerability analysis:
There where several SAIFV's proposed I will be using version 1 as that is the one most closely resembling the XM-1
The turret of the SAIFV has these "mobility or firepower kill" probablities:
Propablity of the 115mm WA threat was 0.2 at 1000m

Probability of the 115mm DU threat was 0.23 at 3000m comming from 0.56 at 2000m so XM774 is not going to be going though the armor of an XM-1 at 4000m at the design angle. So a simple two point average analysis is that the original 1972 armor would protect against XM774 at 2500m.

But by the time of the SAIFV study they where allready asking the question what would it take to increase protection? This is the answer:mRPjnT.jpg

Here we can read that it takes 0.6 tons to give the SAIFV turret front point blank protection against XM774  from the fornt and 1.4 tons give the hull the same protection.
This means that adding 0.9 tons to the turret of the XM-1 is gonna give it a considerable increase in armor protection against XM774.

Now for the rest:

"I use a 60 degree protection cone" This is false I used a 50 degree one for the numbers I provided.

"The 350mm number is completely made up"
Then why is it used on the M1A2 protection scheme (swedish trials) with the same angles as has been provided by the british XM-1 study? Supposidly the number where given at the end of the cold war when US and russia entered into at dearmament agreement. Why 325mm for M60 I don't know maybe its just a mistake that got reprinted.

"M735 can penetrate 380mm of RHA"
At 1524m/s? That would mean it looses 16% of its energy going just 1000m down range that seems unlikely.

"You on the other hand are an Abrams fanboy who doesn't bother to consider alternative interpretations, and considers newspapers more relevant than declassified documents as long as it fits your opinion."
How would you know what I have considered of other interpretations. You on the other hand have selected a study which didn't use XM-1 armor, which was suppose to study the viability of the 105mm and then you dogmatically deny any contradiction evidence. You make up stories with out evidence because you are only focusing on a narrow part of the evidence, because you apparently need it to be true that no part of the Abrams can protect against the XM774. You take the minimal protection level of the crew compartment and demand that it also be the max protection level anywhere on the tank even when we know that attacks ar not spread randomly acros that spectrum but that the front is much more likely to be hit than even at 25 degrees.  And the turret is much more likely to be hit than the hull. So it makes sense to try and distribute the armor to both protect agains the minimum but also increase frontal protection as much as can be allowed. Ultimately we don't know how much wiggle room the requirements gave in the weight allocation department, if there where whishes to frontal protection etc.
How is this for alternative interpretations:

1. Its one of several different ways you can weight the armor scaling between KE and CE protection
2. The different parts of the turret armor has different strength. Like maybe  the Gun Shield has 400mm protection while cheeks has regular protection.
3. Turret armor was upgraded during production so the first tanks have less protection than later ones. Actual weight was over a ton above the projected one on the production line.
4. Its the proposed armor for the M1E1.
5. The CIA randomly mentions it by mistake

The possiblities are plenty.

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6 hours ago, STGN said:

No see you are trying to argue that it is imposible for the Americans to have changed their mind about what protections level even a little bit and you are just so arrogant and condecending that I love pokeing at you becasue your manners are so bad.

 

My dude, as soon as you start framing your arguments with insults you lose regardless of the actual content of your post. I come to this site for discussion not insults. Please stop polluting this forum.

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@SH_MM

 

funny thing is, that real targets that represent T-80 etc was named  M1980 and M1990(expected in year 2000 lol), all of these was simple steel plate without spacing or whatever, just one steel plate(various thicknesses for M80 and M90) at 70°, and nothing wih "uh BRL1 hypothesised T-72" or any other bullshit.

 

as for BRL2 there was description that it was to heavy to fit on real tank, but wasn't much heavier than L2AV has...

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4 hours ago, Zach9889 said:

 

My dude, as soon as you start framing your arguments with insults you lose regardless of the actual content of your post. I come to this site for discussion not insults. Please stop polluting this forum.

Okay so why do you not say that to SH_MM
Are these not insults?:
"What I am doing - and you honestly also should start, if you actually had an interest in finding the truth - is the following:"

 

"What you still massively fail to understand "


"You on the other hand are an Abrams fanboy who doesn't bother to consider alternative interpretations, and considers newspapers more relevant than declassified documents as long as it fits your opinion.

 

If a CIA report says "one version of the Abrams turret", a fanboy's knee-jerk reaction is: "This means that the XM774 cannot penetrate the turret". Meanwhile my first question is: Why did they write "one version of"? How does this fit along with the other sources? What is the context of this statement?"

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23 hours ago, STGN said:

No see you are trying to argue that it is imposible for the Americans to have changed their mind about what protections level even a little bit and you are just so arrogant and condecending that I love pokeing at you becasue your manners are so bad

 

I am not saying that it is impossible for the US Army to change or alter its protection requirements; quite the contrary, I am aware of the fact that they changed some requirements, leading to an increased weight. I am not some sort of America-hater who only keeps arguing to make the US look back; I am interesting in gathering as many informations regarding each tank. I am arguing with you about how, where and when the required protection level was altered and against which type of specific threats it was changed.

 

You came into this discussion - and this forum - practically saying "the M1 Abrams is protected against the XM774 APFSDS and here is why...", but you fail to explain why you believe the M1 Abrams' armor was designed/required to resist the XM774 and your sources are always very vague and leave lots of room for mulitple ways of interpretation.

 

The weight increase related to the altered protection for example is a result of analysis and intelligence gathered from the Yom-Kippur War:

9gV2Qxk.png

 

Now, unfortunately that still leaves lots of room for interpretation and I am rather certain, that you are going to find some way to claim that this is a reference to the need for protection against the XM774 APFSDS; but I'll disagree. The most powerful tank available in the 1973 was the T-62 with its 115 mm 2A20 smoothbore gun. Three types of APFSDS ammunition could be supplied to export customers at the time - 3BM3, 3BM4 and 3BM5 rounds. 3BM3 used a steel penetrator with tungsten-carbide slug, while 3BM4 and 3BM5 were full steel penetrators; the latter featured an improved alloy and tip construction for better performance against sloped armor, but only entered service in 1970 and might not have been available for export before 1973. More modern 115 mm APFSDS such as 3BM21 - and the first 100 mm APFSDS rounds 3BM19 and 3BM20 - where adopted in the Soviet Union in 1972 and not exported before the Yom-Kippur War.

 

That means any lessons learned from the Yom-Kippur War regarding Soviet APFSDS ammunition would be limited to 3BM3, 3BM4 and maybe 3BM5; for a distance of 1,000 meters, the certified penetration by Soviet standards for the 3BM3 is 135 mm steel and 130 mm steel for the steel penetrators respectively, all figures at 60° angle .

 

I believe that - if anything regarding the performance of the Soviet 115 mm APFSDS was assessed - the poor construction and low performance of the early Soviet 115 mm APFSDS ammunition would have only seen as confirmation for the earlier protection requirements. Based on the 1982 CIA report, the initial requirement for the XM1 was based on the assumption, that the T-72 would be able to penetrate 147 mm steel armor at 60° and a distance of 1,000 m - so nothing suggests that any analysis of Soviet APFSDS ammuntion resulting in altered requirements for KE protection.

 

The Yom Kippur War however proved the high lethality of anti-tank guided missiles and RPGs, which lead for example to the Federal Republic of Germany rethinking protection requirements for the Leopard 2 tank and the UK also demanding higher protection against ATGMs in the just started FMBT project. The Washington Post for example opened its 1977 article "Army Leaders Betting Billions That Tanks Aren't Obsolete" with the following sentences: "Early in the Yom Kippur War of 1973, 50 Israeli tanks charged Egyptian infantrymen dug in near the Suez Canal. The Egyptians fired Sagger antitank missiles. Forty of the 50 tanks were knocked out."

 

That the Yom Kippur War revealed ATGMs and - to a lesser extend RPGs - to be of bigger priority than tank vs tank combat has been confirmed by the US Army representatives before Congress:

1yHIYnT.pngOfkoNzh.png

Also note that "protection in mobility" is the primary (!) solution.

 

I don't think that the "reallocation" that a pure reallocation of armor is possible when seeing the changes from the early Chrysler XM1 and the XM1 FSED model. I think it is very reasonable that the changes in the armor coverage did affect the combat weight and that the 58/59 ton weight limit wasn't relevent for the FSED prototypes finally produced in 1978 for the following reasons:

  • the whole point of FSED tanks is to test the tank design, verify that all requirements are met, test the reliability and identify possible shortcomings before comitting to series production - i.e. the second phase DT & OT of the Abrams' program. Three of FSED pilots were later used in 1979 for the RAM-D (reliability, availability, maintainability and durability) tests. Pretty much all their results would be invalid if armor was changed after their production in 1978.
  • in case of the M1IP and M1E1 prototypes, heavier weight was simulated with steel plates. Why did they not add such steel plates to the XM1 FSED pilots, when it already was decided in 1978 for the tank to feature heavier armor?
  • the FSED went into production in Feburary of 1978 and the last one was finished in July 1978. When was the XM1 design altered to include protection?
  • All 14 ballistic hulls and turrets were made as part of the FSED phase and tested between 1978 and 1979. If any armor changes were made after that, then the armor was untested.
  • the final pilot vehicle produced as part of the FSED phase was made in July 1978 and was used for final ballistic acceptance tests in late 1979.

It doesn't make any sense to conduct final ballistic tests (or rather any ballistic tests) when a new configuration of armor has already been decided on and will enter production. So either the US Army decided to invalidate all its test data or the FSED prototypes made in 1978 already were manufactured with the protection changes - and the data delivered to the UK  in April of 1978 - i.e. in the middle production of the eleven FSED pilot vehicles - takes this into account.

 

 

Your source on the whole matter is again far from perfect - it is an article by RAND Corporation (so not direct from the US government), it is not focused on the actual topic but rather on "Transportability in the Defense Department" as its identical name suggests, and the authors are making several mistakes, which contradict with factual information. Zycher and Morton for example write that the XM1 design was finalized in 1975, yet we know that changes to the designs were made in 1976 and both competitor's final designs before the FSED phase were submitted at October 28th of 1976.

We also know that the manufactured XM1 FSED featured the hybrid turret with a gun mount capable of accepting both the 105 mm M68E1 rifled gun and the 120 mm FRG smoothbore gun. The adoption of this turret with an increased weight by 1,000 to 1,500 lbs and was approved only after September 1976. It was not part of the RFP that went out to Chrysler and General Motors, so it was added aftrt 1976. In 1977 it is even stated that the hybrid turret was made part of the DCP:

aABSC2V.png

 

As per Hunnicutt, all FSED pilots had the hybrid turret. So Zycher and Morton are wrong in claiming that the design was finalized in 1975 and your assumption that this meant that the FSED that went into production in 1978 is identical to the 1975/76 design is also wrong. This raises the questions when the protection changes were made and whether "changes made in tank design" means "changes made on the drawing board only that weren't ready for the FSED pilots" or "changes were implemented in the design in time for the FSED pilot production". Given that the 1975 number is wrong either way, we honestly also don't know if the design changes related to ballistic protection were actually made in 1978 and not in 1977 or 1979.


You keep repeatedely using this questionable source as a simple free ticket to discard the declassified British assessment of the XM1's protection from April 1978 and the comments from the April & May 1978 hearings regarding BRL 1 being comparable to the XM1... without your source actually proving that. In theory they also could have finished the design changes to the ballistic protection in January of 1978 or throughout Februrary 1978, so the FSED pilots were ready in time with the correct weight. But since the New York Times called it a 59 tons tank, that cannot be :rolleyes:

 

It is also noteworthy that you claim that this is the proof for reinforced turret armor that can resist the XM774 APFSDS, but Zycher and Morton wrote about "a number of small ballistic protection changes". Completely redesigning the turret frontal armor array doesn't sound like a small change.

 

 

But maybe the increased coverage of the hull and turret frontal armor arrays wasn't the "number of small ballistic protection changes"... even then it is not confirming anything about stronger turret armor against the XM774 APFSDS. For example there was no formal requirement to protect the turret bustle & hull ammo storage of the tank against RPG rounds in 1976, which is why the FRG kept using the thin spaced armor (12 mm steel in front of a 30 mm steel plate with a 50 mm hollow space inbetween) of the earlier Leopard 2 prototypes on the 2AV variant. The Leopard 2AV's turret fully met the US protection requirements according to former Leopard 2 project manager Paul-Werner Krapke; hence another explanation regarding the altered armor protection in reaction to the lessons learned in the Yom Kippur War in order to better resist shaped charge weapons.

 

The XM1 designs already had bulky turret bustle armor, but what exactly do we know about it? Nothing. They even had such armor before Burlington/Chobham was adopted on the tank. For example the "number of small ballistic protection changes" could include altering the armor arrays at these places to provide protection against the 81 mm BRL shaped charge from 90° angle instead of only resisting it at a 45° angle as is the case with the side armor at the crew compartment.

 

23 hours ago, STGN said:

When the pilot tank rolls of the factory floor in 1978 its even called a 59 ton tank:

 

By the public press, which isn't particularly known for being very accurate when it comes to describing pre-production military hardware. Popular Sciences used a drawing of the Leopard 1A3 (!) to represent the Leopard 2AV after (!) the Leopard 2AV had been evaluated by the US Army, Der Spiegel used a Leopard 1A1A1 in 1974 to illustrate a Leopard 2 PT.

 

23 hours ago, STGN said:

So it does indicate that armor was actually added to the turret.

 

It nowhere says that armor was added to the turret! None of your sources say so. From all your sources say the US Army could just as well have reinforced the roof or belly armor! We also have no actual reason to believe that somehow the protection requirement for the turret was raised, but the hull protection requirement was left untouched.

 

... and even if we believed the turret armor protection requirement was raised only, there still is no reason to assume that it was raised to resist the XM774 APFSDS rather than e.g. resisting the XM579E4 from a shorter range. All you say is based on your assumptions, not on your sources.

 

23 hours ago, STGN said:

How about the armor that is actually in the turret, the main pillar of your argument is the claim that the XM-1 had the BRL-1 armor from the 1977 trial where XM774 was able to penetrate BRL-1 at 4000 meters. However apparently you haven't read your own source:

 

I have read the source, as you should do too. I never claimed that the XM1 had BRL-1 armor; I specifically stated that the armor was believed to provide (roughly) equivalent protection and it happens to come from the same designer.

 

It is also nowhere near the "main pillar" of my argument, you seem to forget:

  • BRL-1 is clearly described as roughly comparable to the XM1's armor
  • BRL-2 is clearly described as superior to the XM1's armor protection
  • the declassified British analysis based on the FSED design is not invalidated
  • the SAIFV study is also not invalidated
  • we have still seen no source from you proving that at any point of time protection against the XM774 was required/requested for the XM1

  • we have no source stating that the armor upgrades are focused on the turret

 

23 hours ago, STGN said:

The BRL-1 was a hypothesised T-72 and BRL-2 was a armor that was better than the XM-1:

 

That is not stated in the document. We have again a case of you making assumptions that fit your greater goal rather than sticking to what is written. The BRL designed multiple targets - BRL-1 and BRL-2 as targets consisting of non-convnentional special armor and a further number of conventional targets. The T-72 is represented by one target, but it is not specified to be BRL-1. Likewise it is not stated that BRL-2 is used to represent a Warsaw Pact Tank of the XM1 generation, but it is stated that BRL-2  was used for a special tank designed by a working group with the target to evaluate big the performance gap between the 105 mm M68A1 and the 120 mm FRG smoothbore gun is.

 

23 hours ago, STGN said:

Does that sound like BRL-1 was the NERA and didn't have much KE defence? So how similar was BRL-1 to the XM-1's armor, well according to MR. Stratton it is "roughly the same":

 

Yes, it sounds like BRL-1 was a NERA array. The layout and thickness of an armor array including layers of NERA needs to be specifically designed in order to provide additional performance against kinetic energy rounds. If it is not specifically designed to deal with APDS/APFSDS rounds, it will perform like spaced armor. The original Burlington prototypes designed by the FVRDE provided no additional protection over RHA of the same weight, while being significantly better against shaped charge munitions. As the KE requirement from the US wasn't very demanding and the test round - the XM579E4 - was just like West-Germany's test rounds less effective against even spaced armor, we have little reason to assume that BRL-1 or the M1 Abrams' NERA was actually optimized for additional KE protection over spaced armor.

 

You are just adding your own interpretation, because you want BRL-1 to be something different. As a matter of fact the M1 Abrams' series production armor schemes from the declassified CIA report do not show any optimizations for improved performance against KE rounds. The Leopard 2AV - with its slightly higher KE protection requirement - and the T-72B for example feature armor arrays optimized for higher KE protection (by using thicker steel plates for the NERA sandwiches and additional plates of HHS/anti-KE armor).

 

23 hours ago, STGN said:

Here we can read that it takes 0.6 tons to give the SAIFV turret front point blank protection against XM774  from the fornt and 1.4 tons give the hull the same protection.
This means that adding 0.9 tons to the turret of the XM-1 is gonna give it a considerable increase in armor protection against XM774.

 

The first problem with your argument is that the size difference between the Abrams turret and the up-armored TBAT II turret used in the SAIFV Concepts 1, 2 and 5. The frontal projection of the turret is ca. 55% greater. At the same time, the turret's crew compartment is also more than one feet longer, as it gun intrudes much further into the crew compartment, the gun needs a recoil path and as the commander and gunner sit behind each other rather than side by side. So even the 0.9 tons of weight added to the turret, would not be sufficient to provide a consistent up-armoring as calculated in the SAIFV studies.

 

ws4dAQt.png

The second problem here is obviously the fact, that there is not a single source stating that the weight added as part of "a number of small ballistic protection changes" actually was only added to the turret neither that it was added for improved KE protection. This is again an unproven statement supported by not a single source that you assume to be a fact in order to use it for your next assumption. You keep repeating the same, incorrect pattern for your argumentation. The key problem is that within logic, if you base your assumption on an incorrect (or an unproven) fact, you can argue anything.

 

Is it possible that the weight was added to the turret? Yes, maybe - but we don't know if this was done.

Is it possible that the KE protection was maybe improved? Yes, maybe - but we don't know if this was done.

Do we have any source stating that it was used for this? No, we don't.

 

You are intentionally missing the bold parts and this is the result of your bias rather than logic. It is not a scientifically correct approach to omitt such questions or to ignore sources contradicting them.

 

23 hours ago, STGN said:

There where several SAIFV's proposed I will be using version 1 as that is the one most closely resembling the XM-1
The turret of the SAIFV has these "mobility or firepower kill" probablities:
Propablity of the 115mm WA threat was 0.2 at 1000m

Probability of the 115mm DU threat was 0.23 at 3000m comming from 0.56 at 2000m so XM774 is not going to be going though the armor of an XM-1 at 4000m at the design angle. So a simple two point average analysis is that the original 1972 armor would protect against XM774 at 2500m.

 

This is already based on multiple unproven assumptions about the performance of the armor at different angles (as the constructive angle of the TBAT-II turret with special armor is not identical to the Abrams' turret slope. The turrets do not have any "mobility or fierpower kill" probabilities, the whole vehicles have. There is no specific table for turret, but rather one for the whole vehicle in fully exposed and hull down position. The exact cirumstances of these are also not explained any further; k-kill seems to be specifically demand a direct hit on the ammunition in order for the vehicle to be damaged beyond repair. For example the XM2 - aka the Bradley prototype - has a zero percent chance of catastrophic kill when the hull is not exposed when being hit by a 115 mm APFSDS round. Hence I am fairly sure that the probability tables in the SAIFV study are based on criterias you are not taking into account.

 

A 23% chance of a "mobility or firepower kill" for the SAIFV concept 2 doesn't actually mean the armor is not penetrated; it means neither the gun nor the drivetrain & power pack are hit. The definition for a catastrophic kill in this study is having received a "M and a F kill and [being] damaged beyond repair". Rather than focusing on the crew survivability, only the system survivability of critical components is taken into account.

 

23 hours ago, STGN said:

Then why is it used on the M1A2 protection scheme (swedish trials) with the same angles as has been provided by the british XM-1 study? Supposidly the number where given at the end of the cold war when US and russia entered into at dearmament agreement. Why 325mm for M60 I don't know maybe its just a mistake that got reprinted.

 

You cannot use the Swedish data for what you are trying to prove. The M1A2 protection scheme is absolutely irrelvant to the protection of the XM1. The hull armor was upgraded at least once and the armor arrays were likely changed during the development of the M1IP/M1A1, the M1A1 HA and the M1A2. Also you keep ignoring over and over that RHA equivalent protection is dependent on round. The M1A2 achieving 350 mm KE protection in the 1990s against a very specific round (a 125 mm APFSDS at a very long range, hence impact velocity of only 1,450 m/s) is absolutely irrelvant for the protection achieved in 1978/1979/1980 against a very different threat.

 

LUh9dmD.png

Weight simulator for the improved hull armor of a M1E1. Given improvements in armor technology (and an actual requirement to potentially resist monobloc APFSDS rounds), the protection level achieved by the M1A2 cannot be used for the decade older XM1 Abrams.

 

23 hours ago, STGN said:

You on the other hand have selected a study which didn't use XM-1 armor, which was suppose to study the viability of the 105mm and then you dogmatically deny any contradiction evidence.

 

A "study" that used comparable armor to the XM1 and came to the conclusion (in ballistic tests), that the XM774 can defeat this comparable armor at 4,000 meters distance.

 

23 hours ago, STGN said:

You make up stories with out evidence because you are only focusing on a narrow part of the evidence, because you apparently need it to be true that no part of the Abrams can protect against the XM774

 

You are the last person on this forum that should use the term "evidence". You have continously provided "sources" - and are still doing it - that say absolutely not what you pretend them to say.

 

 "In 1978 a number of small ballistic protection changes were made in the tank design; these changes were significant collectively, raising the total projected weight to 59.8 tons" means to you "the turret armor was reinforced to withstand the XM774 APFSDS" even though the souce doesn't mention the turret, it mentions nothing in regards to improved kinetic protection (or "improving" at all) and it specifically doesn't mention the XM774 APFSDS. You say that "The XM‐l guns will fire a kinetic energy round that Army experts say travels at about a mile a second and can penetrate 15 inches of armor. But not, they add, the new armor." means "It will resist the XM774 APFSDS", even though the XM774 is still in FSED development at the time and not issued to the XM1 tank. Also you ignore that by your logic this tanks should lack the improved armor - as this apparently was added somewhere in 1978, but not when the FSED pilots were produced (Feburary to July 1978), because then the British assesssment and the statements regarding BRL-1 would still remain true...

 

Just show me one source that specifies that the turret frontal armor was improved and one source that shows that the XM1 was actually required to resist the XM774 APFSDS at any relevant point of time. That is the evidence that would be needed to actually start talking about the XM1 being protected against the XM774 APFSDS, rather than deciding-  because of some unique vision, some secret epiphany - that the XM1 must havbe been protected against the XM774 APFSDS round.

 

You still fail to understand that I argue that your sources are not proving what you say, rather than being an America-hater that for dogmatic reasons believes that the XM1 cannot under any circumstances resist the XM774 APFSDS. The actual protection is irrelevant for most of my arguments, my problem is the fact that your sources are so poor and you make up very biased interpretations for extremely vague statements in order to provide "evidence". If you'd distanced yourself from the topic and read your sources word by word, you should notice that none of your sources actually says what you are pretending it would say. Just like none of your sources mentioned a 60° frontal arc protection, yet you started this discussion claiming the (X)M1 had such.

 

So I don't need to hate the Abrams tank or America - I don't hate them. I just need to look at the sources available to me - reliable sources, i.e. declassified documents from different government agencies - and compare them to the "evidence" provided by you in order to find a reason to keep arguing. Just like when in the Leopard 2 thread a user decided to ignore the actual results from ballistic tests (taken from declassified documents), because he prefered to believe vague statements with his very biased interpretation.

 

23 hours ago, STGN said:

 And the turret is much more likely to be hit than the hull. So it makes sense to try and distribute the armor to both protect agains the minimum but also increase frontal protection as much as can be allowed.

 

Hence the declassified British report provides two distances for protection against the XM579E4 APFSDS - protected from 800 m distance on the turret and 1,200 m distance on the hull.

 

23 hours ago, STGN said:

Ultimately we don't know how much wiggle room the requirements gave in the weight allocation department, if there where whishes to frontal protection etc

 

We know the exact requirements for armor protection. We know the exact weight limit initially set, which had to be exceeded in order to implement "number of small ballistic protection changes".  So we know that there was no wiggle room, if even small protection changes require to exceed the weight limit. Even the gun mount compatible with the 120 mm FRG smoothbore gun resulted in the XM1 exceeding its weight limit.

 

__________________________________________________

I don't know if you felt insulted by my previous comments; writting comments on the internet isn't necessarily the best way to transport tone. I don't have any personal problems with you and did not intend to insult you. If you think being called a fanboy is bad, then we have very different experiences regarding insults on the internet. I also don't actually mind your words that Zach seems to consider an insult, because the internet isn't a perfect medium to transport messages.

 

I do however stand by my critique of your research style, as everything provided by you is highly dependent on favourable assumptions in order to make the Abrams look better.

 

I have no interest in dragging this discussion on forever. Either find sources actually saying what you believe they say or stop posting. Also learn to use the quote function of this forum properly; quoting a comment as a whole, then wirting text below with numbers isn't very readable.

 

 

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On 9/21/2020 at 11:14 AM, SH_MM said:

 

A "study" that used comparable armor to the XM1 and came to the conclusion (in ballistic tests), that the XM774 can defeat this comparable armor at 4,000 meters distance.

 

 

I think that rather apparent now. The take away is that RHA is a near useless metric and more confirmation that round design matters a great deal.

 

The armor that the  M1 Abrams had when it was introduced probably wasn't sufficient against Monoblock DU rounds. Knowing what we know now about how much more effective a DU alloy monoblock rounds are against complex armor arrays this shouldn't be as surprising. What these tests show as much of anything, is the much increased effectiveness of rounds like the M774/M833 vs complex spaced arrays vs the previous generation of KE ammunition. 

 

Thankfully the for the M1 the USSR had nothing comparable in design to the M774 until the mid 1980s and IIRC, and  these were not all that common until the last days of the cold war. 

 

Had the cold war gone hot in 1983, the Abrams would have faced mostly 3bm-22 type rounds and earlier. I suspect (but don't know) based on the small amount of data available that the M1 would have had some protection against these rounds.

 

 

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