M1A2 SEPv3 on the move.


With Rheinmetall presenting smoothbore that is 130mm Eurosatory next month I really hope those weight simulators are not for the new armor package only. The Abrams turret cannot even longer support a ...



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Some random comments on reddit about M1A2 SEPv3 on the move.

  • With Rheinmetall presenting 130mm smoothbore on Eurosatory next month I really hope those weight simulators are not for the new armor package only.
  • The Abrams turret cannot even support a longer 120 mm gun, fitting a 130 mm gun will be impossible. Also Rheinmetall expects the gun to be ready somewhere 2020-2030, while the M1A2 SEP v3 is expected to be delivered in 2017.
  • OK, what are ammunition developments then? Aside from M829A4 that is. SEP v3 has ADL, but airburst ammo was available since M830A1, so what is that for? New German/Israeli ammo, or new US designs?
  • The M830A1 doesn't have a proper airburst capability, just a proximity switch for engaging helos. The US Army will buy an US-made round, the XM1147 from ATK , even though it would be cheaper to buy available ammunition from other countries. According to above link, the XM1147 will replace four already existing rounds, I think this should be the M830 HEAT-MP, the M830A1 MP-AT, the M908 HE-OR-T and the M1028 carnister round. There are some ongoing rumors about the US Army adopting the XM360 gun of the Future Combat Systems on the Abrams in the near future. However the M1A2 SEP v3 prototypes all use the old M256 gun.
  • Cool, thanks. I am right now reading all I can find about XM360E1. SEP v3 might not feature it yet, but it does not mean there isn't M1A3 somewhere in the near future.
  • Source on the Cannot Support part? It was my understanding that the US preferred the shorter barrel for urban combat, and preferred to use better ammo for its penetration
  • The US tests of the German L55 gun predates the US experiences with urban combat by a decade. Originally the US developed (together with Germany, the UK and France) a family of 140 mm smoothbore guns - the US version, made by Watervilet Arsenal, was called the XM294 gun. The 140 mm gun would not fit into the Abrams directly, so a 120 mm L55 gun was also developed - this gun was tested on the Component Advanced Testbed (CATTB tank). However the Congress cut the funding for the development of the XM294 gun (including the 120 mm gun), after the program consumed too much budget without moving forwards. Following the cancellation of the XM294, the US Army approached Germany/Rheinmetall to test the 120 mm L55 gun being developed for the Leopard 2. Three guns were bought by the US and designated M256E1 after some US specific changes. Twelve further barrels were locally produced by Watervilet Arsenal. The testing of the three guns fitted to M1A2 tanks lasted from 1998 to 2000. It was discovered that there are certain incompabilites between the Abrams and the German gun. While the M256 gun is a version of Rheinmetall's original L44 gun, it has been modified because the US wanted a cheaper and less complex weapon system, that was compatible with the Abrams design and already existing components used in the Abrams. The German L55 gun however is designed to fit into the same gun mount as the German L44 gun and to have the same center of mass. The M256 has a different gun mount, a different recoil system, a modified barrel with different center of mass and is mounted much further away from the turret ring than the German weapon. US testing at least revealed that the accuracy took a massive hit, specifically on the move, when the M1A2 was using the M256E1 tank gun. The longer barrel with different center of mass caused too much oscillations for the stabilization system. Also the higher recoil impulse and recoil mass was too much for the existing system. An attempt to solve this problem was using parts of the XM294 gun development, namely the DTS (Dynamically Tuned Shroud) to reduce barrel vibrations. When using a DTS, the thermal shroud and bore evacuator of the gun barrel are not fixed to the gun barrel or gun mount, but rather are fixed in a "free floating" arrangment, so the DTS can act as counterweight to the gun vibrations. A major problem with the DTS was that the technology was not mature enough. It broke down very often, even during the first test on the actual tank without firing a single shot. In general, the L55 gun could be fitted to the Abrams when accepting the loss of accuracy. If you google a bit, you should be able to find a proposal from General Dynamics to develop a completely new stabilization system for the M256E1 gun, as the old one was to bad. Paying for a new stabilization & recoil system, while redesigning the Abrams turret to accomadate everything was not an option. It was too expensive for the Army's budget, after the Congress already terminated the XM294 gun for budget reasons. So in ot's current form, the Abrams cannot support a L55 gun. The above is mostly based on a book from the German author Rolf Hilmes, who not only served on a tank and studied engineering, but also worked for the military procurment agency as tank technology specialist and was to a certain extent involved in the development of the 120 mm L55 gun. and preferred to use better ammo for its penetration You are misinterpreting something. The US Army originally wanted the L55 gun, because without the added velocity, the M829A2 APFSDS was incapable of defeating a certain US/NATO target representing the future Russian armor. The M829A3 managed to destroy the same target when fired from the M256 gun. However the M829A3 does not provide equal or better penetration than a modern APFSDS fired from a L55 gun. That's not possible.
  • However the M829A3 does not provide equal or better penetration than a modern APFSDS fired from a L55 gun. That's not possible. Ammunition design is more important than going from 5.3 m to a 6.6 m barrel. A 120mm DM63 only gains 7% more muzzle velocity fired from the L55 (I assume at ~ 20 degrees C), while the KEWA2 gains between 7% and 3% more muzzle velocity (depending on propellant temperature). Based on Lanz-Odermatt a M829A3 out of an L44 will easily outperform a 120mm DM63 out of an L55. Of course I would take this with a grain of salt since Lanz-Odermatt is only valid for homogeneous targets, homogeneous rods, and the U and W alloys used in the M829A3 and 120mm DM63 are not the same as the ones used to derive Lanz-Odermatt.
  • Ammunition design is more important than going from 5.3 m to a 6.6 m barrel. A 120mm DM63 only gains 7% more muzzle velocity fired from the L55 (I assume at ~ 20 degrees C), while the KEWA2 gains between 7% and 3% more muzzle velocity (depending on propellant temperature). First of all, you are making a very wrong assumption. The relation between armor penetration and muzzle velocity is NOT linear. The relation between armor penetration and kinetic energy is linear for a given projectile. The relation between kinetic energy and muzzle velocity is of the second order. In general, the L55 barrel increases muzzle energy by 15%, which will directly translate to about 15% higher penetration. Based on Lanz-Odermatt a M829A3 out of an L44 will easily outperform a 120mm DM63 out of an L55. No. Your problem lies in trying to explain the performance of modern tank ammunition using a formula designed to only estimate the performance of monobloc penetrator with very specific alloys. The Lanz-Odermatt formula also requires input for several unkown factors, which has to be " guesstimated " or invented by the user. This is why the Lanz-Odermatt formula is very crappy and pretty much biased depending on the user's specific input. Want M829A3 to be better than DM63? Use a slightly longer penetrator (800 mm+) and slightly lower deceleration (50-60 mps). Want DM63 to be better in Lanz-Odermatt? Assume that it has a slightly longer penetrator (700 mm+) and the M829A3 a slightly shorter one (700 mm+). Odermatt is dependent on values which can only be estimated. That is bad. However what users of the Lanz-Odermatt formula ignore, is that we are not in 1982 anymore. Penetrator technology has evolved, just like armor has evolved from homogenous steel over spaced armor to composite armor. Nobody uses dumb monobloc penetrators anymore, for which the works from Lanz and Odermatt are valid. In Germany it started with the adoption of the DM33 APFSDS in 1987. A special tip design increased the armor penetration against certain types of armor by more than 10%, granting the DM33 equal or better penetration than the M829A1, despite calculations with Lanz-Odermatt would imply otherwise. The M829A3 for example is said to use a special 100 mm long anti-ERA tip , because this improves penetration against targets with heavy ERA by 20-30%. The fact that the penetrator then has to be 100 mm shorter than what the average Lanz-Odermatt user assumes will decrease the armor penetration against steel. Germany uses in the DM53/63 a segmented penetrator design as implied by patents, [Poland has made the development of a segmented penetrator public]( www.dtic.mil/ndia/2011ballistics/11441.pdf ). Depending on exact design, segmented penetrators can offer greatly improved penetration against all types of armor. On modern APFSDS even the materials have a composite approach! South-Korea uses a composite tungsten design with two different alloys to allow self-sharpening like DU while retaining certain favourable characteristics of tungsten. TL:DR: We don't know the exact dimensions and values for any modern penetrator, which is why Lanz-Odermatt's formula can be abused for biased values We know that Lanz-Odermatt's formula is only valid for monobloc penetrators, as used at the time Lanz and Odermatt were involved in the development of the Swiss 140 mm gun We know that (at least some) modern APFSDS are not using the old monobloc penetrator design, so Lanz-Odermatt is no applicable Furthermore: We know that the DM63 from the L55 gun has a much greater muzzle energy We know that the M829A3 has a greater weight and larger fin diameter, so it will travel longer and loose more energy while traveling through the air Alone the last two points make it pretty much impossible for the M829A3 to beat the DM63. Sure, you can tweak the numbers in such a way, that Lanz-Odermatt allows you to calculate a higher penetration for the M829A3, but this doesn't really say a thing. On the other hand you also can tweak the numbers in such a way that the DM63 penetrates more armor.
  • The relation between kinetic energy and muzzle velocity is of the second order. In general, the L55 barrel increases muzzle energy by 15%, which will directly translate to about 15% higher penetration. I'm making no mistakes here because I wasn't talking about penetration, I was talking about the diminishing returns you get from increasing tube length. Furthermore penetration does not increase linearly with kinetic energy at impact for long rod penetrators, a linear increase with velocity is much more reasonable. No. Your problem lies in trying to explain the performance of modern tank ammunition using a formula designed to only estimate the performance of monobloc penetrator with very specific alloys. The Lanz-Odermatt formula also requires input for several unkown factors, which has to be "guesstimated" or invented by the user, which is why the Lanz-Odermatt formula is very crappy and pretty much biased depending on the user's specific input. Want M829A3 to be better than DM63? Use a slightly longer penetrator (800 mm+) and slightly lower deceleration (50-60 mps). Want DM63 to be better in Lanz-Odermatt? Assume that it has a slightly longer penetrator (700 mm+) and the M829A3 a slightly shorter one (700 mm+). Odermatt is dependent on values which can only be estimated. That is bad. Except the lengths and diameters of the M829A3 and 120mm DM63 are roughly known, the M829A3 is significantly longer, thicker, and heavier. Lanz-Odermatt is the best publicly available formula on this subject. Do you have a better model than L-O? IIRC 50 m/s to 60 m/s is closer to what older 105mm APFSDS ammo would experience, newer ammo has better BC, there is a paper on this from DTIC somewhere on my disk but I'm too lazy to find it. nobody uses dumb monobloc penetrators anymore, for which the works from Lanz and Odermatt are valid. A already mentioned this caveat in my original post. My argument is that ammo design is more important than some minor increases in muzzle velocity due to increased gun tube length, this supports my argument. The M829A3 for example is said to use a special 100 mm long anti-ERA tip, because this improves penetration against targets with heavy ERA by 20-30%. This entire argument hinges on the weight of the sabot petals. There are cutaway photographs of the A3 sabot petals and they are only slightly longer than than A2 petals. There is very little chance that the A3 sabot petals are 1.25 times heavier, the cutaway photographs make it clear only very little material was added between the A2 and A3 versions. The fact that the penetrator then has to be 100 mm shorter than what the average Lanz-Odermatt user assumes will decrease the armor penetration against steel. Your linked .PDF shows that segmentation can increase penetration depth into homogeneous targets. On modern APFSDS even the materials have a composite approach! South-Korea uses a composite tungsten design with two different alloys to allow self-sharpening like DU while retaining certain favourable characteristics of tungsten. No doubt that modern W alloys are improving, so are modern U alloys. We know that the M829A3 has a greater weight and larger fin diameter, so it will travel longer and loose more energy while traveling through the air How do you know that the 120mm DM63 has a shorter fin span? The length of the M829A3 shifts the center of pressure from the fins (relatively) rearward and should allow for smaller fins. The 120mm DM63 does have a better finesse ratio but the M829A3 is slower out of the muzzle (drag force is quadratic at this Reynolds number) and has a better BC. This is all pretty inconsequential in the greater scheme of things, both rounds lose very little velocity out to their maximum effective range. Alone the last two points make it pretty much impossible for the M829A3 to beat the DM63. The best evidence we have does not support this conclusion. Lanz-Odermatt may not be valid for complex penetrators and complex targets but this in no way advantages the 120mm DM63 over the M829A3, in fact "heavy" penetrators like the M829A3 would show superior real world performance to light ones due to their mechanical robustness and their resistance to yaw. A 120mm DM63 out of an L55 has only 1.125 times more muzzle velocity than a M829A3 out of an L44 but it its rod is roughly 0.786 times the mass, the 120mm DM63 and M829A3 have nearly the same kinetic energy out of the muzzle. It is possible that the 120mm DM63 has better materials or a better design that allows for more penetration against complex targets, it is also possible that the M829A3 has better materials or a better design. The point is that given what is publicly avilable on long rod penetration the M829A3 is superior based on its physical dimensions (which count for a lot BTW).
  • I'm making no mistakes here because I wasn't talking about penetration, I was talking about the diminishing returns you get from increasing tube length. And you pretended that lengthening the barrel increases performance by 7%, which it doesn't. Except the lengths and diameters of the M829A3 and 120mm DM63 are roughly known, the M829A3 is significantly longer, thicker, and heavier. No. What is known is the length and diameter of the M829A3 and DM63 projectiles , the Lanz-Odermatt formula however uses the length and diameter of the penetrator . Major difference in penetration performance can be achieved by using only slightly different values in the equation. One cannot accurately judge from the overall length and diameter to the penetrator's IRL size accurately. The M829A1 for example has an overall length of 780 mm, but only a 684 mm long penetrator - that's a 13% (or 96 milimetres) smaller penetrator. The German DM33 introduced one year earlier however has a 640 mm long projectile, with a penetrator length of about 580 mm - that's only a 9.37% smaller penetrator (overall about 60 mm shorter). So tell me, how do you come up with somewhat exact results for the pentrator length? Is the M829A3's penetrator (if it had a monobloc penetrator) 9% shorter than projectile or 13%? Or somewhere inbetween? For the DM63 the same question arrives. It is very easy to tweak the numbers in favour of one or the other round with Lanz-Odermatt. Lanz-Odermatt is the best publicly available formula on this subject. No. It's the best publicly available formula on the subject " penetration of 1980s monobloc penetrators into semi-infinite steel ". That's a different subject . IIRC 50 m/s to 60 m/s is closer to what older 105mm APFSDS ammo would experience, newer ammo has better BC, there is a paper on this from DTIC somewhere on my disk but I'm too lazy to find it. You remember wrong. Official data from Rheinmetall on the DM53 and DM63 claims only a deceleration of 55 mps per km upto a range of 5,000 m. For the M829A2 the deceleration is 59.5 mps per km until an unkown distance. Soviet APFSDS designs originally lost up to 140 mps per km, but the latest types are somewhere in the 60s. The M829A2 however has a much lower trajectory than the M829A3, so the M829A3 should perform a bit worse. A already mentioned this caveat in my original post. My argument is that ammo design is more important than some minor increases in muzzle velocity due to increased gun tube length, this supports my argument. In what world does this support your argument? " Germany using stone-age ammo with a long gun barrel, while the US uses high-tech stuff from a shorter one " is not true. The current DM63 is newer than the M829A3. So your argument fails. This entire argument hinges on the weight of the sabot petals. There are cutaway photographs of the A3 sabot petals and they are only slightly longer than than A2 petals. There is very little chance that the A3 sabot petals are 1.25 times heavier, the cutaway photographs make it clear only very little material was added between the A2 and A3 versions. The argument is based on ATK patents, which you ignore. That the 3 kilograms weight are probably not made up - in fact it comes from a presentation on the advantages of composite materials from the US Army Laboratories, which has been referenced on several other forums like WoT forums and SteelBeasts. The length increase from M829A2 sabot to M829A3 sabot is about 20% (see here ). The M829A3 however also has a thicker rod, which increases the sabot diameter and thus the needed material. The M829A2 has a diameter of about 22 mm, which translates to a 69.11 mm circumference - the thicker 25 mm diameter of the M829A3's projectile/penetrator has a circumference of 78.54 mm, which equals an increase by about 12%. Your linked .PDF shows that segmentation can increase penetration depth into homogeneous targets. Yes, but the M829A3 doesn't follow the segmented approach. It's one dense penetrator + one steel tip, not as shown in the files from the Polish WITU research agency a number of dense penetrators (tungsten) + steel spacers. No doubt that modern W alloys are improving, so are modern U alloys. South-Korea did actually test US DU ammunition during the development of the K2 Black Panther. The M829A3 has been imported in single digit quantity. The best evidence we have does not support this conclusion. Lanz-Odermatt may not be valid for complex penetrators and complex targets but this in no way advantages the 120mm DM63 over the M829A3, in fact "heavy" penetrators like the M829A3 would show superior real world performance to light ones due to their mechanical robustness and their resistance to yaw. Again you are trying to enforce Lanz-Odermatt's formula and "real world performance" of monobloc penetrators onto non-monobloc penetrators. It doesn't work like this. Segmented penetrators have proven to perform better against spaced, ceramic and reactive armor arrays than conventional monobloc penetrators. A 120mm DM63 out of an L55 has only 1.125 times more muzzle velocity than a M829A3 out of an L44 but it its rod is roughly 0.786 times the mass, the 120mm DM63 and M829A3 have nearly the same kinetic energy out of the muzzle. The muzzle energy of the DM53/63 is depending on temperature nearly at 13 MJ, while the M829A3's muzzle energy is only at 12.09 MJ. Any sort of attempt to calculate the muzzle energy of the in-flight projectile or the penetrator requires more exact values for the component weight than any of us can find. So unless you want to attempt discussing the component weights, DM53 & 63 are favoured here. Using the values for penetrator weight found on German forums for the DM63 and the penetrator estimate from the blog (to which I earlier linked to) for the M829A3, the M829A3 has only about 7.3 MJ muzzle enerhy and the DM63 has about 8 MJ. The point is that given what is publicly avilable on long rod penetration the M829A3 is superior based on its physical dimensions (which count for a lot BTW). No, it isn't. It's superior based on the assumption that the penetrator has a length of X, whereas X has to be chosen to a certain margin higher than the penetrator length estimation Y for the DM63. If X is not larger by that margin than Y, then Odermatt-Lanz will provide higher penetration values for DM63. Also you try to ignore velocity, which matters just as much as the length. In fact for a given L/D ratio of 30 and a constant energy of 10 MJ, it matters quite a bit more than length to reach optimal penetration.
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