STGN

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?"

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:

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:

It even says in Hunnicutt that it was weight REALLOCATION:

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


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:

And what was the difference between BRL-1 and BRL-2 again:

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":

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:

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.

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.

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.

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 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.".

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.

3 minutes ago, Wiedzmin said:

is that geometry is hard for your understanding? i don't see any reason why photogrammetry of real tank + measures check + pics of ripped of M1A1 sides is doesn't give you a chance to check all "LOS" that you need(especially when you can check where the plate is, where the hatch is etc), or you just god of 3d models and can make it more accurate than real tank ?

 

i think remembered you, you was on defenceforumindia ? 

is that your scheme ?

 

same question 

 

have you ever seen any real factory blueprints lol ?

 

well, why don't you make your own ? to prove that everything is wrong ? 

 

you trying to protect your believes, i'm not interested in that, if you want really discuss i'm interested, but all i see now, "all you data is from GJ!1" but i showed you that i used only external plates thicknesses, and you keeps put your fingers in your ears....

 

oh funny thing, i though you was doing that, because i can't see any real arguments  

 

 

just to be clear, if you really want discuss "how we will get accurate LOS" ok go, i'm interested, if you keeps insists "oh all your pics a shit, because i think mine better" well, no go...

1. Oh great because you don't realize that you can actually test out an hypothesis about size and volume using 3d. Things have to fit together you know.

2.Great, yes. And yes I did make that, based on what I knew at the time. If you are going to be pointing out that it is not 100% right, then I already know that as I have updated my knowledge since then.

3. I did, what is the point here?

4. Yes I have.

5. I never said "everything is wrong" I said it is "mostly wrong", sure you got the outside right, however you put alot of numbers on the inside, we already know the outside of the tank, its the inside that is the interesting part.

6. Maybe you should be looking at the mirror to answer the question who is protecting their beliefs.

7. Right even as I went through all the logic of my argument you can't see anything.

8. I never said all your pics are shit. That is something you have chosen to read into it. I specifically criticized the composition and LOS of your drawing of the Abrams left side turret armor. 

33 minutes ago, Wiedzmin said:

i use only GJ thickness of external plates, all other i get from photogrammetry and measures, what else you don't understand ?

 

source ?

scaling of schemes... good luck

 

i'm not interested in protection levels

 

and ? i have high-res on that pics it's not secret, and they match photogrammetry 

 

good luck to you with your hollywar

 

 

p.s and please do not confuse the words "argument" and "personal opinion", because all your "arguments" is just your words, without any sources or proves 

1. Oh wow you got internal measurement from photogrammetry, you must be a genius. 

2. Can you see the images I posted or is there some magic spell called 105mm that completely changes the design of the turret, you do know that the turret was designed for the option to be upgraded, right?

3. Yeah we all know that the worst source for information is official drawings. But I look forward to your photogrammetry of the inside of the armor.

4. Yeah put your fingers in your ears and yell lalalalal, because there is no corrolation between armor dimensions and protection level I guess.

5. And? there you have the source which you have just confimed is in line with your photogrammetry.

6. Which holy war? You mean that I argue, that in order to achieve the desired protection level the armor has to be thicker than what you "guessed", so as I am arguing that the armor is less effective than what you want it to be, and I am waging a holy war?
 

7. You obviously don't know what an argument is, because you are the one just posting a picture putting on values with out having any evidence or logic behind it.

7 hours ago, SH_MM said:

 

The drawings included in the official CIA document are not for scale. The confirmed measurements do not match with each other and depending on what value one chooses as references, differences in scaled/estimated armor thickness in excess of 100 mm are possible.

 

 

The XM774 wasn't adopted as in 1978, so it cannot be stated as a fact that the New York Times article refers to it. XM774's adoption was delayed to FY81 due to production issues.

 

Based on the Special Armor IFV studies of the Infantry FIghting Vehicle Task Force (from which you apparently took the penetration values for the XM579E4 and the XM774), the XM1 Abrams was not designed to withstand the XM774 APFSDS. According to the vulnerability analysis done by the BRL, the concepts 1, 4 and 5 - all of which were designed with protection equivalent to the XM1 tank - were protected against the 115 mm APFSDS (WA) only, which was simulated using the XM579E4 APFSDS. The hull and turret front could be defeated by the 115 mm APFSDS (DU) fired from one kilometer distance (no shorter distance was used for this analysis).

 

To increase protection against the 115 mm APFSDS (DU) as simulated by the XM774 APFSDS along a frontal 50° arc, new armor arrays were designed based on the same technology as used on the XM1 tank. These armor arrays were 6 tons (concept 1) or 5.3 tons (concepts 4 and 5) heavier than the original XM1 level armor array.

 

 

These steel equivalent protection values are very much irrelevant, as they are highly dependent on round. We know from the hearings regarding the adoption of the 120 mm smoothbore gun in front of a subcommittee of the US Congress, that the BRL-2 special armor target provides more protection than the XM1 tank's armor, which was described as roughly equivalent to the BRL-1 special armor target. The XM774 was tested against BRL-1 and the results weren't bad.

 

We also know that the 120 mm growth potential rounds from the FRG and the UK - i.e. prototype versions of the DM23 and L23A1 APFSDS modified for the US - managed to defeat BRL-2 at the tested ranges. As the DM23 has only 400 mm penetration into steel at 200 m based on the German measuring methodology according to declassified British documents, this make the CIA armor values rather questionable.

 

 

The British declassified documents, German declassified documents, the SAIFV study and the Swedish leaks confirm that the US had a requirement for full armor protection only along a 50° frontal arc.

 

 

No offense, but this is well known and has been posted here already months ago.

1. I agree that the images in their original state are a bit skewed. However when you apply the correct external dimension and internal(center of gun rotor) you get the same values that Gaijin measured on the outside of plate thickness. they also correspond to other measurements on the outside of the tank like distance between front of front plate and weld line of the hull array. Plus you get the same LOS when you measure on SAIFV drawings and the British computer drawings. So I think they are actually pretty accurate.

2. I have to clarify I think the front turret can withstand the xm774 not the hull. You are quit right I have read the report many times.

3. Maybe the steel equivalent values are "irrelevant" however my point was that when you are designing after a specific threat once you have an armor that can defeat it then you can just apply it, and when you calculate the numbers you find that the steel LOS is similar for arears that is suppose to defeat the same threat.

4. The 400mm number from CIA seems to be obviously based on the XM774 also there is a difference in how the Germans measure armor and how the Americans measure armor. I don't recall reading the DM23 400mm claim at what angle was the steel, it penetrated?

5. You are quit right about all these documents, however its the turret front we are interested in here not overall protection.

9 hours ago, Wiedzmin said:

 

 Maybe you should read something before posting ? especially part about "M1(M1 105mm)" ?

 

my estimations ONLY for M1, why you trying to show me M1A1 and M1A2 ? 

 

try to start with arguments, i'm really not interested in reading wall of text without any arguments, with all respect.

 

for my estimates i used WT outer plates thicknesses that they posted in developer diary, because they used USG, so all these measures are correct.

 

for whole frontal part estimate i used photogrammetry of whole M1 and some measures that get from modelers(armorama site etc), i also used M1 dimensional scheme, and all that measures are coincided

 

 

 

 

as for 4inch frontal plates is often quoted in US sources, so at the moment i use that value, maybe you can give us USG of internal plate ?

or on what source all your claims is based ?

 

here is scheme showing production stages of M1 turret, so it's have same spacers as hull front, and i think overall same structure, and it corresponds with CIA scheme + i'm not tried to get "REAL SIKRIT SPECIAL ARMOR SCHEME!11" only thickness of frontal part.

 

as for your "armour values" investigation, BRL1 during trials was penetrated by XM774(26mm diam core) from 3km, and it's claimed that BRL1 target was 10% tougher than real M1, but i'm not interested in any armour calculations at the moment.

 

So, you registered here for reasonable discussion with proofs, or just to chat about that "in some game everything is not right! I think so! but I'm not sure ..." ?

 

On 9/8/2020 at 10:22 AM, Wiedzmin said:

 

some of my estimations on M1(M1 105mm) left turret frontal part, used all known and available data at the moment and some photogrammetry of real M1 from museum...

This is mostly wrong dimensionally and conceptually.
Where to start... I am guessing that you are basing your drawing on Gaijin's measurements of the Minnesota Abrams combined with the CIA drawing of the hull front armor? First of all I am sure they got the front armor volume wrong because they thought they measured from the edge of the internal armor plate sticking out through the underside of the turret on the right side. However this is a miss conception we can easily see this in images from the underside during production. What they are actually measuring from is the "armor floor plate" the plate that carries the armor, that is why we don't see any weld lines and it is curved rather than sharply angled like two welded RHA plates would be:


This points to another misconception about the Abrams front turret armor rear plate, that it is monolithic. However it is not a straight copy an past of the hull front armor, rather it is a mix of front and bustle armor. The Abrams is rather similar to the Leo2 in this regard. A "thin" back plate to maximize the adjustability of the armor protection. Here the similarity ends, because to this back plate bolts can be fastened enabling you to mount the number of armor plates needed to reach the desired protection level.

So how can we estimate the LOS of the Abrams turret front? Well we go back to the front hull and fist we get the right dimensions from that. Now I happen to have the exterior dimensions of the Abrams, but we could scale of the dimension that Gaijin have provided us of 22" from front to start of back plate. And in the end up with a Armor LOS of ~650mm which is a damn coincidence cause that is also the LOS of Leopard 2 hull armor(and turret I estimate). So now we know the minimal LOS needed with Abrams armor to meet the armor requirements of 322mm+ KE/ 636mm+ HEAT.

Given that the turret had to meet at least this same requirement we can just add ~650mm LOS to the side of the left turret cheek at the correct angel. Here I am unsure whether they went with 25 or 30 degrees but it actually don't make much difference, what you end up with is a ~800mm frontal LOS with either. But now we know the frontal LOS which by the way is roughly in the middle range of the Gun Shield LOS of 710-855mm. This gives us a minimal LOS of ~570mm rather than ~500mm on the left cheek. And we can use that to estimate the right side armor LOS. The right side of the turret have a shallower sweep but houses all the most important equipment of the tank so it makes sense to copy the frontal LOS rather than the 25-30 degree LOS to achieve a uniform protection from the front. Now if you put all that in to a 3d Program you will see that everything starts matching up really nice with photos, GPS housing, real dimensions and the ones we find in CIA documents and Army technical papers.

Scaling the array composition we of cause also have to take offset in the numbers we can find in official documents and the CIA drawings.
When you scale the armor drawings you find that they have similar amounts of steel LOS at the appropriate angles.
The Gun Shield has a 6" back plate(part of the rotor) a ~1,3" LOS plate(probably not steel), 12,5" deep Special Armor(SA) array and a 1,6" plate angled at 33 degree obliquity giving 2" LOS
The Hull front has a 5,8 LOS backplate(110mm plate) ~12" deep SA array and a 1,3" plate at 49 degree obliquity giving ~1,65" LOS.
Hull side is pretty similar despite missing SA.

We know that the hull front could defeat the XM579E4 APFSDS(at 1470 m/s) but not the XM774 APFSDS 
XM579E4 could penetrate 161mm RHA at 60 degree obliquity (322mm LOS)
XM774 could penetrate 189mm RHA at 60 degree obliquity (378mm LOS)

BTW (322+378)/2 = 350 , probably where the 350mm figure stems from.

And now we have to decide how to interpret the given information.
The Army tells us in  New York Times, march, 1978 that the Abrams can not be penetrated by its own round, which is capable of penetrating 15"(380mm, XM774) of armor.
CIA documents tells us that one version of the Abrams turret has 400mm-KE 750mm-CE protection
UK tells us 25 degree XM579E4 protection is principal
others say 30 degree 350mm protection.

How I read this is that the steel LOS of Gunshield with SA LOS of hull is likely how the front cheeks are armored. However it might just be similar to the hull in composition.

Turret side armor over the crew compartment looks different but is really just the hull armor scaled to 65 degree obliquity. Instead of the 3 SA tri plates being angled relative to the outer plate they are lying parallelly to the plate.  The rear plate being ~2,49" thick LOS at 25 degree angular is ~150mm(~5,9") with the outer plate being 19mm that is ~45mm(1,8") LOS.
My estimation of side LOS is 400mm rather than Gaijin's 381mm, I think they missed the fact that the roof plate is recessed down into the interior side plate.

Turret bustle has thicker LOS of about 441mm and while it has probably bad KE protection head on it will likely provide better protection than the front armor at 25-30 degrees angular.