Contemporary Western Tank Rumble!

[SH_MM]

 

M833 - 360-370 mm

[heretic88]

This is whole chart is strange... 360-370 should be M774... M833 should definitely penetrate more than 400mm.  430-440 (where M900 is on the chart) is more believable for it. Armor values are also off. "T-62 basic" looks like a T-62M with metal-polymer blocks. T-72A and M1 should have the exact same protection...

[SH_MM]

1 hour ago, heretic88 said:

This is whole chart is strange... 360-370 should be M774... M833 should definitely penetrate more than 400mm.  430-440 (where M900 is on the chart) is more believable for it. Armor values are also off. "T-62 basic" looks like a T-62M with metal-polymer blocks. T-72A and M1 should have the exact same protection...

 

The chart is correct. The labeling might be a bit confusing: the T-72M1 referenced in the table is not the basic T-72M1 (i.e. Object 172M-1-E5 or Object 172M-1-E6) but rather the T-72M1M (Object 172M-1-E7),  which is a T-72M1 with the more advanced NERA armor of the T-72B. Later this was export variant was superseded by the T-72S (Object 172M-1-E8) as true export model of the T-72B. At least on T-72M1M tank was operated by the Republic Guard in Iraq. Rheinmetall marketed its 105 mm smoothbore guns as capable of defeating the T-72M1M (aswell as the T-72S and T-72B), which the normal 105 mm rifled guns L7 and M68 were incapable of doing. They tried to persuade the US Army to buy smoothbore guns for the Stryker MGS among others.

Due to its rarity, the existence of the T-72M1M remained unknown for some while and I haven't seen any clear data to whom exactly how many T-72M1M tanks were sold.

 

I don't think that the "basic" belongs to the T-62 version, but rather is meant to show that this is the basic threat for which the mentioned APFSDS ammunition was adopted. The values clearly reflects the T-62M.

 

As for the penetration achieved by the M833 APFSDS: 400 mm against steel armor at normal combat ranges is not possible. The length and velocity of the longord penetrator are not enough to achieve such levels of performance. I.e. the M833 has a 427 mm long penetrator, as you can see in the following images:

 

The following graph taken from a declassified document shows the reduction of the velocity of several APFSDS types over ranges. As one can see, the impact velocity of the M833 APFSDS at 2,000 metres (typical combat range used to measure armor penetration) will be slightly below 1,400 m/s.

The following charts shows a comparison of different methods for measuring normalized penetration (i.e. LOS penetration against a sloped target) in relation to the length of the high-density longrod penetrator of an APFSDS round. It compares two mathematical solutions (the forumula from W. Lanz & W. Odermatt aswell as a sub-module of the ALEGRA software suite) with actual measurements (the dots) which are interpolated using a polynomial fit (spline interpolation).

Looking at the chart, the length and velocity of the M833 would roughly result in a factor slightly below 0.8 penetrated steel thickness per penetrator length (P/L). A value of 0.8 multiplied with 427 mm will result in an estimated armor penetration 341 mm. Keeping in mind that the graph below is calculated for tungsten rods, the DU penetrator might (based on the exact criteria) perform better; the US Army Research Laboratory (ARL) has established that there is no difference in armor perforation (punching a hole through a steel target), but a difference for armor penetration (punching a hole into a steel target without fully perforating it) - so it isn't really clear wether this matters. Earlier work from ARL suggested a 8-10% lower penetration for tungsten rods, which would suggest 360-370 mm penetration (or rather 180-190 mm sloped at 60°) at 2,000 m distance. 

 

 

[heretic88]

Thanks for the explanation!

 

So, what do you think where does the 500mm for the M833 (in Militarysta's chart, and also in some russian sources) comes from? And what criterias did they use to determine such result?

[Militarysta]

Ok, so I should correct this tabel in case M833, Mathos proofs convinced me.

How about DM13 and DM23?

@Methos?

 

 

[Militarysta]

18 hours ago, heretic88 said:

Thanks for the explanation!

 

So, what do you think where does the 500mm for the M833 (in Militarysta's chart, and also in some russian sources) comes from? And what criterias did they use to determine such result?

No idea, most of them are taken from Bauman book (2006 Moscow) and they are put ther based on "unkown" criteria. Thats the problem whit, in theory realible sources.

Whit polish WITU is the same - sometimes they put something shamefully mistaken but generally it's good source.

[heretic88]

1 hour ago, Militarysta said:

No idea, most of them are taken from Bauman book (2006 Moscow) and they are put ther based on "unkown" criteria. Thats the problem whit, in theory realible sources.

Whit polish WITU is the same - sometimes they put something shamefully mistaken but generally it's good source.

What if they just made some typo? Maybe that data is for the M900 and for some reason they wrote M833 instead?

[Lord_James]

On 8/11/2018 at 6:07 PM, SH_MM said:

 

M833 - 360-370 mm

 

2 things: 

 

1. Source? 

 

2. Is this chart suggesting that M900 is only as powerful as M111 Hetz? Cause M111 could penetrate the T-72 at range (just barely), but the graph also shows M900 just barely penetrating a T-72 at range. 

[Ramlaen]

I thought M111 could only penetrate the hull of an early T-72.

[SH_MM]

4 hours ago, Militarysta said:

How about DM13 and DM23? 

 

Based on the graphs you posted earlier, the 120 mm DM13 and 120 mm DM23 APFSDS have rather short penetrators, but also a rather large diameter. This is relevant, since penetration increases with diameter for a given length (more accelerated mass = more kinetic energy; penetration scales with kinetic energy). A slightly thinner rod with greater length would overall be superior, but technology and/or other requirements resulted in a diameter of 32 mm for the DM23 APFSDS (thinner tungsten rod with the available alloys did shatter too often).

 

The velocity of the DM23 after traveling 2,000 m is 1,529 m/s according to Swiss firing tables, but these list the muzzle velocity at only 1,640 m/s. So either the DM23 has a muzzle velocity of 1,640 m/s rather than the usually reported 1,650 m/s or the differences are caused by the Swiss measuring methology or are result of a local modification to the 12 cm PzKan 87 (Swiss designation for the DM23). If the latter cases are true, the impact velocity should be ~1,539 m/s instead.

Given that the penetration efficiency of shorter, thicker rods is more, it seems that the DM23 might achieve a penetration per length of above 1 against German HzB A steel:

(from Anderson and Riegel III, 28th International Symposium on Ballistics, "Estimate of penetration/perforation performance based on semi-infinite penetration data")

 

The problem is that exact informations regarding the specific steel alloy are rather scarce. HzB. A (and other steels of the HzB classification) existed in several versions with different alloys and hardness levels. In so far it is hard to convert the exact penetration data into RHA penetration. For the graph from the previous post, the steel hardness was said to be 255 on the Brinell scale.

 

Based on the plotted data, the DM23 might achieve between ~ up to 1.05 P/L, so its 360 mm long penetrator would result in a penetration of 378 mm into semi-infinite HzB. A steel. I don't have access to the source from which the data is taken (research paper by Hohler and Stilp, who apparently work for the German Fraunhofer institute), so it is unknown to me wether the steel target was sloped or not. The penetration against sloped targets would be higher than unsloped ones. As this is semi-infinite penetration, the perforation should be higher (meaning: DM23 would probably punch a hole through a 390 mm thick  HzB. A steel plate under the same conditions).

 

 

As for the 120 mm DM13: It is hard to say due to its unconventional construction. The BM-42 Mango APFSDS (which seems to be the closest thing in terms of internal penetrator construction) supposedly achieves a penetration slightly greater than the combined tungsten penetrator length; it has a higher muzzle velocity, but due to the fin construction a greater V-drop (Fofanov lists V-drop of Soviet 125 mm APFSDS ammo as between 60 and 140 m/s/km; given that Mango has full calibre fins, it should be significantly more than 60 m/s/km). Maybe the steel sheat helps increasing the penetration efficiency by simulating a thicker rod/lower L/D ratio?

 

The DM13 should have slightly above 1,500 m/s velocity at 2,000 m distance according to the US graph from the last post (probably 1,510 - 1,520 m/s). That and its shorter rod should lead to a lower penetratioon than DM23 by quite a bit... how much? I don't know. Maybe it is 320-350 mm, if the steel has any positive effect on armor penetration. Otherwise it would again be close to a P/L of 1 (if DM13 behaves like a conventional monoblock penetrator), which would lead to a penetration of only ~310-320 mm. Perforation and penetration against sloped targets might again be higher.

 

The penetrators of both the M833 and the 120 mm DM23 APFSDS have rounded tips, which performs slightly worse than flat-tipped penetrators against sloped target (but penetration still should be higher than against unsloped ones). 

 

1 hour ago, Lord_James said:

1. Source?  

 

2. Is this chart suggesting that M900 is only as powerful as M111 Hetz? Cause M111 could penetrate the T-72 at range (just barely), but the graph also shows M900 just barely penetrating a T-72 at range. 

 

Source is a Rheinmetall presentation from 2002. It used to be on DTIC, but I cannot find the full presentation at the moment... maybe the link expired or it was removed...

 

The M111 Hetz was capable of penetrating the original T-72's hull armor at very short ranges (some sources say 500-800 metres maximum). The T-72 had a glacis consisting of 80 mm steel, 105 mm stekoplastika (glass-fibre reinforced plastic) and 20 mm steel sloped at 68°. The T-72A had a different layout: 60 mm steel - 105 mm stekoplastika  - 50 mm steel (this is also 10 mm more steel), which was more effective against AP(FS)DS ammo. On later models, a 16 mm thick steel plate was added to the hull, improving protection further. The late production model of the T-72A featured spaced hull armor.

 

The M111 Hetz could never defeat the turret armor except for maybe a direct hit near the gun mount, where the armor thickness was only ~300-350 mm. The turret reaches a thickness of more than 475 mm at the well armored cheeks.

[LoooSeR]

Small Grammar nazi (or Grammar commisar?) note - not stekloplastika, but stekloplastik. 

[SH_MM]

9 minutes ago, LoooSeR said:

Small Grammar nazi (or Grammar commisar?) note - not stekloplastika, but stekloplastik. 

 

I am innocent, S. Zaloga used the false form in "M1 Abrams vs T-72 Ural".

[LoooSeR]

12 minutes ago, SH_MM said:

I am innocent, S. Zaloga used the false form in "M1 Abrams vs T-72 Ural".

lol, i think that fiberglass layer is called Steklotekstolit (STB).

   Kind of terrible (for our tankers) thing is that T-72B3 still have unmodified armor from whatever T-72 they took for modernisation. I even saw T-72A (?) in one of TV reports about army training in the field. Strange to see that after so many years info on armor of Soviet tanks is still partially relevant.

[Mighty_Zuk]

You can use both. Steklotekstolit just means it's some composite material and not entirely fibreglass, while stekloplastik means just fibreglass. 

[Liberator]

16 hours ago, SH_MM said:

 

Based on the graphs you posted earlier, the 120 mm DM13 and 120 mm DM23 APFSDS have rather short penetrators, but also a rather large diameter. This is relevant, since penetration increases with diameter for a given length (more accelerated mass = more kinetic energy; penetration scales with kinetic energy). A slightly thinner rod with greater length would overall be superior, but technology and/or other requirements resulted in a diameter of 32 mm for the DM23 APFSDS (thinner tungsten rod with the available alloys did shatter too often).

 

The velocity of the DM23 after traveling 2,000 m is 1,529 m/s according to Swiss firing tables, but these list the muzzle velocity at only 1,640 m/s. So either the DM23 has a muzzle velocity of 1,640 m/s rather than the usually reported 1,650 m/s or the differences are caused by the Swiss measuring methology or are result of a local modification to the 12 cm PzKan 87 (Swiss designation for the DM23). If the latter cases are true, the impact velocity should be ~1,539 m/s instead.

Given that the penetration efficiency of shorter, thicker rods is more, it seems that the DM23 might achieve a penetration per length of above 1 against German HzB A steel:

(from Anderson and Riegel III, 28th International Symposium on Ballistics, "Estimate of penetration/perforation performance based on semi-infinite penetration data")

 

The problem is that exact informations regarding the specific steel alloy are rather scarce. HzB. A (and other steels of the HzB classification) existed in several versions with different alloys and hardness levels. In so far it is hard to convert the exact penetration data into RHA penetration. For the graph from the previous post, the steel hardness was said to be 255 on the Brinell scale.

 

Based on the plotted data, the DM23 might achieve between ~ up to 1.05 P/L, so its 360 mm long penetrator would result in a penetration of 378 mm into semi-infinite HzB. A steel. I don't have access to the source from which the data is taken (research paper by Hohler and Stilp, who apparently work for the German Fraunhofer institute), so it is unknown to me wether the steel target was sloped or not. The penetration against sloped targets would be higher than unsloped ones. As this is semi-infinite penetration, the perforation should be higher (meaning: DM23 would probably punch a hole through a 390 mm thick  HzB. A steel plate under the same conditions).

 

 

As for the 120 mm DM13: It is hard to say due to its unconventional construction. The BM-42 Mango APFSDS (which seems to be the closest thing in terms of internal penetrator construction) supposedly achieves a penetration slightly greater than the combined tungsten penetrator length; it has a higher muzzle velocity, but due to the fin construction a greater V-drop (Fofanov lists V-drop of Soviet 125 mm APFSDS ammo as between 60 and 140 m/s/km; given that Mango has full calibre fins, it should be significantly more than 60 m/s/km). Maybe the steel sheat helps increasing the penetration efficiency by simulating a thicker rod/lower L/D ratio?

 

The DM13 should have slightly above 1,500 m/s velocity at 2,000 m distance according to the US graph from the last post (probably 1,510 - 1,520 m/s). That and its shorter rod should lead to a lower penetratioon than DM23 by quite a bit... how much? I don't know. Maybe it is 320-350 mm, if the steel has any positive effect on armor penetration. Otherwise it would again be close to a P/L of 1 (if DM13 behaves like a conventional monoblock penetrator), which would lead to a penetration of only ~310-320 mm. Perforation and penetration against sloped targets might again be higher.

 

The penetrators of both the M833 and the 120 mm DM23 APFSDS have rounded tips, which performs slightly worse than flat-tipped penetrators against sloped target (but penetration still should be higher than against unsloped ones). 

 

 

Source is a Rheinmetall presentation from 2002. It used to be on DTIC, but I cannot find the full presentation at the moment... maybe the link expired or it was removed...

 

The M111 Hetz was capable of penetrating the original T-72's hull armor at very short ranges (some sources say 500-800 metres maximum). The T-72 had a glacis consisting of 80 mm steel, 105 mm stekoplastika (glass-fibre reinforced plastic) and 20 mm steel sloped at 68°. The T-72A had a different layout: 60 mm steel - 105 mm stekoplastika  - 50 mm steel (this is also 10 mm more steel), which was more effective against AP(FS)DS ammo. On later models, a 16 mm thick steel plate was added to the hull, improving protection further. The late production model of the T-72A featured spaced hull armor.

 

The M111 Hetz could never defeat the turret armor except for maybe a direct hit near the gun mount, where the armor thickness was only ~300-350 mm. The turret reaches a thickness of more than 475 mm at the well armored cheeks.

Lol M111 penetrating glacis T-72A(60 mm steel+105 mm stekloplastik+50 mm steel) at distance 1500-2000 m( ОКР Отражение). 

only after welding a 16 mm high hardness plate could protect the T-72A from M111 at an impact speed of 1428 m / s

[SH_MM]

A few days ago the folks from Warthunder went to Minnesota and measured some details regarding the physical thickness of the armor of an original M1 Abrams tank, something which was already mentioned in the United States Military Vehicle General topic.

 

 

The English version of the article can be found here. I decided to take these values and combine them with the schmatics of the original composite armor (aka "Chobham", "Burlington" & "BRL-1") fielded on this version to estimate the overall armor thickness. The scan quality of these schematics is low (the paper wasn't flat when scanned, so the lines are not always straight), but I tried to adjust for this as good as possible. It seems that these schematics are not for scale or the measurements were wrong (though that doesn't seem likely).

 

Overall it seems that the armor thickness has been exaggerated quite a bit; some people said it would be 700 mm or even 750 mm, but most results end up being below 600 mm. I guess the most damning argument against the overall thickness being in the 650-750 mm range is the claim, that the distance between weld lines on the hull floor is just 22 inches (558 mm). Even though it isn't clear wether this includes or excludes the weld lines, it more or less means that overall cavity thickness is way below 558 mm. Add to this a 101 mm backplate and a 31.75 mm frontplate (both sloped) and 700-750 mm armor thickness becomes impossible, IMO 650 mm aswell, but I've never seen exact angles for the LFP and the hull floor.

 

 

WT also measured the thickness of the turret's armor cavities, but they didn't mention if that includes slope and they didn't mention the exact thickness of backplate, but it also doesn't seem to warrant the 700-800 mm thickness sometimes claimed. Armor cavity thickness was 19.5 inches on an unspecified side of the turret (the horizontal slope of the turret front is assymetrical), but the front plate is 1.5 inches (38.1 mm) thick.

[SH_MM]

 

Threats and simulated weapons during the Abrams' development, giving a rough idea about armor protection. From otvaga, unfortunately the full source wasn't posted.

[skylancer-3441]

On 10/28/2018 at 2:35 PM, SH_MM said:

From otvaga, unfortunately the full source wasn't posted.

IFV Task Force Study results (1978-04), chapter VIII (Appendices), Appendix E - BRL Vulnerability Analysis of the IFV concepts, page 2. More there

[Scav]

Hello, first time posting here (long time lurker), I'd like to continue the discussion on the leo 2 etc.
 

On 8/5/2018 at 8:08 PM, Militarysta said:

BTW - Im not sure DM-13. In green book (Bauman 2006 Moscow) is 220mm/60@ but IMHO it could be overestimated. From the other side - some other polish Autors found  in british archves that "unkown" german 120mm KE was able to penetrate 450mm steel from 1km in late 70's... so maybe..

I know of the Bauman book, though most of those seem to be estimates at best, the only other source I know of that could depict DM13 is this slide:

Spoiler

Though this is from January 1974, atleast 5 years before the introduction of DM13, though it might be an experimental version of DM13, it does seem quite different (not to mention 5 years of ammo development could mean quite a sizeable difference example: DM23 -> DM33).
The diameter and the diameter of the penetrator don't seem to line up either, which is very weird....

It seems that it can defeat a HS (Heavy Single, 150mm at 60°) at 2500m, with a vΔ of 105m/s per 1000m this would mean an impact velocity of around 1490m/s, so extrapolating that data to PB would give us around 178mm at 60° (rough estimation).

 

This seems quite similar to M735 (forgive me, using WarThunder value for 60° here, I think it's largely correct) though XM735 in this picture only seems to defeat HS plate at around 800-1200m.....
Not quite sure what to think of this.

 

Could you provide me a link or a picture to the British document mentioning that "120mm KE" round?
DM13 overall seems like a very odd design, taking mutiple other designs and combining them...
 

[Belesarius]

9 minutes ago, Scav said:

Hello, first time posting here (long time lurker), I'd like to continue the discussion on the leo 2 etc.
 

I know of the Bauman book, though most of those seem to be estimates at best, the only other source I know of that could depict DM13 is this slide:

  Reveal hidden contents

Though this is from January 1974, atleast 5 years before the introduction of DM13, though it might be an experimental version of DM13, it does seem quite different (not to mention 5 years of ammo development could mean quite a sizeable difference example: DM23 -> DM33).
The diameter and the diameter of the penetrator don't seem to line up either, which is very weird....

It seems that it can defeat a HS (Heavy Single, 150mm at 60°) at 2500m, with a vΔ of 105m/s per 1000m this would mean an impact velocity of around 1490m/s, so extrapolating that data to PB would give us around 178mm at 60° (rough estimation).

 

This seems quite similar to M735 (forgive me, using WarThunder value for 60° here, I think it's largely correct) though XM735 in this picture only seems to defeat HS plate at around 800-1200m.....
Not quite sure what to think of this.

 

Could you provide me a link or a picture to the British document mentioning that "120mm KE" round?
DM13 overall seems like a very odd design, taking mutiple other designs and combining them...
 

Welcome to SH!

 

[Collimatrix]

16 minutes ago, Scav said:

Hello, first time posting here (long time lurker), I'd like to continue the discussion on the leo 2 etc.
The diameter and the diameter of the penetrator don't seem to line up either, which is very weird....
 

 

Perhaps it's a sheathed penetrator, and one number is the diameter of the inner tungsten penetrator, while the other number is the tungsten penetrator plus outer steel cladding?

[Scav]

Just now, Collimatrix said:

Perhaps it's a sheathed penetrator, and one number is the diameter of the inner tungsten penetrator, while the other number is the tungsten penetrator plus outer steel cladding?

Yes, from what I know that's true, but the values don't match the ones I've been able to find:

Spoiler

 

And it's more than just sheathed, it's also segmented with a weirdly designed ballistic cap and the first actual "penetrator" part seems to be similar in function to the ones found in 3BM15 etc (though substantially larger and with a tip reminiscent of L23A1).

Spoiler

 

[Scav]

27 minutes ago, Belesarius said:

Welcome to SH!

Thanks great general of Justinius .

[SH_MM]

22 hours ago, Scav said:

Though this is from January 1974, atleast 5 years before the introduction of DM13, though it might be an experimental version of DM13, it does seem quite different (not to mention 5 years of ammo development could mean quite a sizeable difference example: DM23 -> DM33).
The diameter and the diameter of the penetrator don't seem to line up either, which is very weird.... 

It seems that it can defeat a HS (Heavy Single, 150mm at 60°) at 2500m, with a vΔ of 105m/s per 1000m this would mean an impact velocity of around 1490m/s, so extrapolating that data to PB would give us around 178mm at 60° (rough estimation). 

 

This seems quite similar to M735 (forgive me, using WarThunder value for 60° here, I think it's largely correct) though XM735 in this picture only seems to defeat HS plate at around 800-1200m.....

 

The data used by Warthunder for the M735 is simply wrong. It is not possible for the M735 to penetrate the same amount of armor as the DM13 APFSDS at the same distance, given that penetrator length is essentially identical (~313 mm vs 315 mm), but the muzzle velocity and length-to-diameter ratio are in favor of the 120 mm DM13. An older article published in 1982 in the US ARMOR magazine suggests that the XM827 (German 120 mm DM13) has a 20% larger penetrator mass and was able to defeat all targets during the 1976 gun trials by NATO at longer ranges than the M735 (the M735 failed to penetrate some targets).

 

Given the higher drag of the DM13, the M735 might be able to reach the same level of armor penetration at ranges greater than 4 kilometres (assuming deceleration stays constant up to this distances), but the 105 mm rifled guns M68 & L7 weren't considered accurate enough (neither was the 120 mm Rh 120 L/44 firing 120  mm DM13 ammunition).

 

22 hours ago, Scav said:

DM13 overall seems like a very odd design, taking mutiple other designs and combining them...

 

The layout of 120 mm DM13 is identical to a patented design from 1972.

 

Patent drawing from patent DE2234219, registered on 12th July 1972. They certainly couldn't take design aspects from other APFSDS ammunition which didn't exist at the time.

 

22 hours ago, Collimatrix said:

Perhaps it's a sheathed penetrator, and one number is the diameter of the inner tungsten penetrator, while the other number is the tungsten penetrator plus outer steel cladding? 

 

AFAIK the table posted earlier was made by another internet user, who based it on a (de)classified report. He might have made some error when entering the numbers from the paper into the computer, because the DM13's penetrator diamter is listed as larger than the actual diameter of the sub-projectile, which is physically impossible. The penetrator diameters for the L15 APDS, the L52 APDS and the 110 mm APDS are all smaller than the projectile diameter - just as expected.

 

22 hours ago, Scav said:

And it's more than just sheathed, it's also segmented with a weirdly designed ballistic cap and the first actual "penetrator" part seems to be similar in function to the ones found in 3BM15 etc (though substantially larger and with a tip reminiscent of L23A1).

 

The weirdly shaped ballistic cap is in fact a windshield and a very normal design. Several other APFSDS rounds from NATO and the Soviet Union (among them the L23A1 APFSDS, Lekalo and Mango) use the same method to connect the windshield to the penetrator.

The penetrator design and working mechanism is not similar to the Soviet 3BM-15 APFSDS and its sucessors. The Soviets used very brittle tungsten-carbide cores, which were shaped like bullets and embedded into the steel, because they would break otherwise.

 

The tungsten-carbide tips would break off when hitting sloped armor or become damaged when penetrating spaced armor, which significantly reduced the performance of Soviet APFSDS. That is why the tungsten-carbide core was later moved to the rear of the penetator to deal better with spaced and composite armor arrays.

3BM-26, the tungsten-carbide penetrator is located in the fin-section.

 

The DM13 APFSDS uses a penetrator made of WHA; the patent from 1972 suggests that 95% tungsten, 3.4% nickel and 1.6% iron would be desirable. The steel sheat is only added, because of the low yield strength of the WHA, which breaks apart when hitting (highly) sloped armor. The steel sheat apparently doesn't extend over the frontal (separate) section of the penetrator, because the tip always breaks off when impact sloped targets. Furthermore this layout was found to be advantageous against multi-plate armor arrays, as the larger frontal portion would result in a larger hole, through which the main part of the penetrator could travel without being damaged.

[Scav]

49 minutes ago, SH_MM said:

The data used by Warthunder for the M735 is simply wrong. It is not possible for the M735 to penetrate the same amount of armor as the DM13 APFSDS at the same distance, given that penetrator length is essentially identical (~313 mm vs 315 mm), but the muzzle velocity and length-to-diameter ratio are in favor of the 120 mm DM13. An older article published in 1982 in the US ARMOR magazine suggests that the XM827 (German 120 mm DM13) has a 20% larger penetrator mass and was able to defeat all targets during the 1976 gun trials by NATO at longer ranges than the M735 (the M735 failed to penetrate some targets).

Interesting, I was assuming that they managed to improve on the M735 since the tests from that table, guess not much or not at all?
IIRC XM827 was supposed to be DU which at this point was probably superior due to alloys being better, might explain the difference?
 

59 minutes ago, SH_MM said:

They certainly couldn't take design aspects from other APFSDS ammunition which didn't exist at the time.

Well, I didn't mean that they took those aspects from other rounds, but that they used similar design features as present on other rounds (later ones).

A bit similar to how 3BM32 has the same general exterior shape as DM13.

I do wonder what the purpose of these features was.

 

1 hour ago, SH_MM said:

AFAIK the table posted earlier was made by another internet user, who based it on a (de)classified report. He might have made some error when entering the numbers from the paper into the computer, because the DM13's penetrator diamter is listed as larger than the actual diameter of the sub-projectile, which is physically impossible. The penetrator diameters for the L15 APDS, the L52 APDS and the 110 mm APDS are all smaller than the projectile diameter - just as expected.

That explains a few things I found curious.
 

1 hour ago, SH_MM said:

The weirdly shaped ballistic cap is in fact a windshield and a very normal design. Several other APFSDS rounds from NATO and the Soviet Union (among them the L23A1 APFSDS, Lekalo and Mango) use the same method to connect the windshield to the penetrator.

It seemed quite thick at the front end to me, I guess most pictures or renders of APFSDS don't quite do justice to the thickness of the windshield.

Intriguing how they left a small section hollow at the front, I realised that the attachment area to the actual penetrator was probably just that, but the empty space there seems out of place.

 

1 hour ago, SH_MM said:

The penetrator design and working mechanism is not similar to the Soviet 3BM-15 APFSDS and its sucessors. The Soviets used very brittle tungsten-carbide cores, which were shaped like bullets and embedded into the steel, because they would break otherwise.

Yeah, I just figured the penetrator seemed segmented and had a weirdly shaped front section, almost as if it was supposed to penetrate the first couple of layers and then leave a rather large hole for the second segment to follow up on.
Purely speculation ofcourse.

 

1 hour ago, SH_MM said:

The tungsten-carbide tips would break off when hitting sloped armor or become damaged when penetrating spaced armor, which significantly reduced the performance of Soviet APFSDS. That is why the tungsten-carbide core was later moved to the rear of the penetator to deal better with spaced and composite armor arrays.

Yeah, though they also used some kind of tungsten tip in combination with the tungsten core in some of the later versions (3BM22 IIRC).
 

1 hour ago, SH_MM said:

The DM13 APFSDS uses a penetrator made of WHA; the patent from 1972 suggests that 95% tungsten, 3.4% nickel and 1.6% iron would be desirable. The steel sheat is only added, because of the low yield strength of the WHA, which breaks apart when hitting (highly) sloped armor. The steel sheat apparently doesn't extend over the frontal (separate) section of the penetrator, because the tip always breaks off when impact sloped targets. Furthermore this layout was found to be advantageous against multi-plate armor arrays, as the larger frontal portion would result in a larger hole, through which the main part of the penetrator could travel without being damaged.

Could you potentially give a link or something?
I've been scouring the internet for any kind of info on this round and what it's supposed to be capable of, but to no avail, I was just left with more questions in the end.
95% tungsten seems on the low end, would explain why they thought a more complex shape was necessary...
 

Thanks for the info though, that's very interesting and in line with some of my suspicions!