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Thanks to all that responded to my question about the Jagdpanzer E-50.

Now for another silly question. The monster American T-95 is armed with a 105mm gun, which is pretty good, but wouldn't it be possible that after encountering panzers like the TigerIII, Maus, and E-100 that the Americans would shoehorn a bigger gun into that hull?

I'm thinking of using a 120mm L/60 M1 anti-aircraft gun as the basis, a simular gun was used on the M-103 tank destroyer of the 1950's and 60's. With such a gun, I figure the T-95 would have a better chance fighting those German monsters. Besides, why should the Nazis have all the fun of having scary warmachines!

Of course this could lead to a "hypothetical weapons design" arms race, with the German fans wanting to cram 15cm flak cannons into their vehicles!!

What do y'all think?

Yes, absolutely!

For HE rather than AP, I might suggest the US 155 mm gun M2 (taking a barrel from GHQ's US71 or US80) or the 8" howitzer M1 (barrel from GHQ's US79). The rate of fire would suffer, but these would be magnificent bunker busters.

I think the race is already on. Consider Su152 (historical) and Kampfwagenvernichter E90 (Krokodil) with 17 cm gun.

Don S.

I can't speak for the hypothetical / alternate "Wehrmacht 1947" timeline, but it might be illuminating to examine the actual, real-world timeline on this subject.

The "T-95" was known earlier in its development as the T28 Heavy Tank. This vehicle had the heaviest armor of the US Army experimental heavy tanks of the 1940s. But there were others in the T series.

The T26 we all know. It became the M26 Pershing.

The T28 heavy tank was later reclassified as the T95 self propelled gun.

The T29 was a turretted heavy tank intended to be the equal of the Tiger II. It was developed in parallel to the T28. It mounted the same 105mm gun as the T28 in a massive turret. The hull was used as a test bed for several other T experiments. One was the T34, which mounted a 120mm gun (derived from the anti-aircraft gun). The M103 Heavy Tank was a direct decendant of this development effort, with a new turret that used the same 120mm gun that was mounted in the T34 in 1947.

The T30 was a further test bed heavy tank program, mounting a 155mm T7 gun derived from the Long Tom, in an enlarged turret with an extra crewman.

The development of the T28, T29, T30 and T34 were started in 1944. The T28 and T29 prototypes were finished by early/mid 1945. The T29 was briefly ordered into production after the fall of Germany, in anticipation of the invasion of Japan. But that order was soon cancelled. I believe the development program was completed in 1947.

Heavier German armor had been anticipated in 1944, and the 105mm, 120mm and 155mm guns were ready to go into heavy tanks. So yes, I believe that US Army Ordnance was in a position to quickly upgun the T28 ("T95") if and as needed.

Quick by US Army standards, that is.

Hope that helps.

OK for 155mm gun but it needed a new AP shell.

The standard AP 112 shell (APCBC/HE) was credited with 160mm (500 yds) and 152mm (1000yds) against homogenous steel at 30° and 25mm kess against hardened fsce steel.

The 90mm T15E1/L71 would penetrate 220mm of homogeneous steel at 1000 yards.

I think the British would have been willing to share their Armor Piercing Discarding Sabot technology (nearly 4000 ft/s - 1200 m/s from the 17 pounder). Since the Germans had limited supplies of tungsten and uranium, the Allies had a decided advantage here.

Don S.

TAMMY wrote:OK for 155mm gun but it needed a new AP shell.

The standard AP 112 shell (APCBC/HE) was credited with 160mm (500 yds) and 152mm (1000yds) against homogenous steel at 30° and 25mm kess against hardened fsce steel.

Hmmm. Maybe if you are shooting at the Tirpitz.

But shooting at a tank, I'm not so sure. Yes, having sufficient penetration is a great boon to anti-armor effectiveness of a given shell. But it is not the only variable in the story.

A solid hit by a medium-velocity 155mm shell is likely to take any tank of the 1940s out of action. Even when they did not penetrate, Soviet 152mm hits were known to remove tracks, optics, and even the turrets of Tigers, sometimes simply lifting the turrets out of the race, other times displacing the turrets several feet (images of Tigers with their turrets on the engine deck are available from Soviet archives). Tiger crews were known to suffer concussions, deafness, blindness, and dis-orientation after 152mm hits.

The Tiger (Tiger I) had the best quality steel armor composition of any German tank. After 1943 the plate quality went downhill on German tanks, due to the pressing need to simplify production and shortages of certain metals(particularly nickel).

Lower quality armored plates on Panthers (same quality or better than used on Tiger IIs) were observed to shatter from overmatching AP or large caliber HE hits, or from repeated non-penetrating hits by lesser caliber guns. In some cases the glacis or the turret front fell off of the tank.

It was in large part due to their rather extensive wartime experience with these effects that the Soviets used larger caliber tank guns than the West throughout the Cold War, despite having developed super high velocity 57mm and 85mm guns by 1944/45.

As "Uncle Joe" was quoted as saying, "Sometimes quantity has a quality all it's own." This was evidently true not only in the numbers of battalions, but also in the caliber of guns.

The 90mm T15E1/L71 would penetrate 220mm of homogeneous steel at 1000 yards.

I would take any US Ordnance testing results or penetration specs from the WW2 and immediate post-war era with a large grain of salt. They do not correlate well to the testing / specs of other nations. This seems based primarily on the "standard" RHA plate that Ordnance used, which was substantially inferior in its resistance to penetration compared to most nations' armor plates.

This was one significant contributor to the "gunpower deficit" of US AP ammunition in 1944. The M10's 3-inch gun and the Sherman's 76mm gun could easily penetrate the front armor of a Tiger or a Panther at reasonable combat ranges ... according to Ordnance. But not according to the Germans.

Donald M. Scheef wrote:I think the British would have been willing to share their Armor Piercing Discarding Sabot technology (nearly 4000 ft/s - 1200 m/s from the 17 pounder). Since the Germans had limited supplies of tungsten and uranium, the Allies had a decided advantage here.

The British did indeed share their APDS tech with the US. The US was not interested.

Let us not forget that in the real-world timeline, even with the threat of Soviet T-55s and T-10s, the US 90mm-armed M46, M47 and M48 tanks of the 1950s did not use APDS ammunition.

US HVAP projectiles were quite frankly superior to British APDS by the end of 1945, and remained highly competitive throughout the 1950s. The British did not really solve the dispersion problem of their APDS throughout the life of the 17 pounder -- beyond about 500m it was literally a "hit or miss" affair, with a high percentage of misses against stationary targets on quiet ranges with experienced gunners. The US HVAP rounds were shown in gunnery trials to be the most accurate tank rounds available, up through the first half of the service life of the 20 pounder.

It was only with the maturation of the 20 pounder that British APDS ammunition clearly surpassed US HVAP, so that with the adoption of the British-designed 105mm L7 gun the US was finally convinced to make the transition to sabotted projectiles.

Kill that man, he knows too much.

av8rmongo wrote:Kill that man, he knows too much.

More likely just talks (and types) too much. Maybe I should switch to decaf ....

Personally I'd like to see more verifiable data on 17pdr APDS; quotes from gunners, WO reports and so on. The vast majority of data in print and on line seems to base its entire credibility on the Isigny test of August 1944, and even in that report the assumption was that the ammunition had not been proof tested and did not represent the true accuracy of the round. My concerns are based on the notion that the 17pdr was meant to be effective at standard battle ranges (1000m), so it makes no sense to make a round that is only accurate to half that range. What makes this notion even more dubious is that the round clearly worked well for the 6pdr, that HVAP (APCR) was a known performer and could well have been substituted for the 'failing' APDS round... in short, to me there is a lack of credibility in an assertion that the round was so pathetically innacurate; it does not fit the surrounding data.

piersyf wrote:Personally I'd like to see more verifiable data on 17pdr APDS; quotes from gunners, WO reports and so on. The vast majority of data in print and on line seems to base its entire credibility on the Isigny test of August 1944, and even in that report the assumption was that the ammunition had not been proof tested and did not represent the true accuracy of the round.

Pre-Issigny US Testing:

The initial US Army testing of British APDS was for the 6pdr, prior to D-Day. The test was of anti-armor effectiveness, rather than accuracy. Many weapons were test-fired against a variety of available German tank targets, including US 37mm guns, bazooka 2.36" rounds, 75mm WP and 105mm HE rounds. The primary tank targets were Pz III -- showing just how far behind the US Army was in assessing the German armor threat.

The results of the 6pdr APDS test firings were not included in the conclusions of the report by the US Army testers, as the rounds were so innaccurate that they were not able to gather sufficient hits for penetration data. They very generously concluded that they must have been too inexperienced in using the round, and urged that British gunners should be available for any subsequent testing of APDS.


US Testing: Issigny, July/August 1944:

Target: Panther Tank, Frontal Aspect

Only 24 of 42 APDS rounds hit the (stationary) target at 200, 400 and 600 yard ranges.

The gun was operated by experienced British Army gunnery crew. It was subsequently asserted that the results indicated that the ammo was from a poor lot, and further observed that the case the ammo came in did not indicate that the lot had been proof-fired.


British Testing: 17 pdr accuracy testing, described in W/O 291/1263 and WO 165/135, recorded on 22nd September 1944:

Target was a British "standard" target, which I believe was 1 yard by 3 yards (about the same size as the frontal aspect of a Churchill turret).

400 yds
APC hit 90.5%
APDS hit 56.6%

600 yds
APC hit 73.0%
APDS hit 34.2%

800 yds
APC hit 57.3%
APDS hit 21.9%

1000 yds
APC hit 45.3%
APDS hit 14.9%

1500 yds
APC hit 25.4%
APDS hit 7.1%

“… useful range of APC ammunition was 900 yards while that of APDS was only 450 yards.â€￾

My concerns are based on the notion that the 17pdr was meant to be effective at standard battle ranges (1000m), so it makes no sense to make a round that is only accurate to half that range. What makes this notion even more dubious is that the round clearly worked well for the 6pdr, that HVAP (APCR) was a known performer and could well have been substituted for the 'failing' APDS round... in short, to me there is a lack of credibility in an assertion that the round was so pathetically innacurate; it does not fit the surrounding data.

The British Army accepted lower accuracies than US Army across the board. Even the 17pdr APC would have been rejected by US Ordnance. But wartime APDS was a non-starter for the US, no matter how many ways they tried to test it.

US testing went so far as putting US projectiles into 17pdr cases to try to get the gun to achieve US expected levels of accuracy.

It may sound like I am "diss'ing" the British APDS. I'm not. The Brits loved their APDS, even while they worked on it's accuracy problems. They had more combat experience than the US Army in mid-1944, and were a bit closer to the Soviet view of "better is the enemy of good enough" on the accuracy of their guns. Even with very accurate guns, gunners would often miss in the stresses of combat. But when they DID hit, they REALLY WANTED their hits to make a difference.

But the British also were repeatedly impressed by the accuracy of US guns. Right up through the end of the war there are British expressions of appreciation for the accuracy of the US M3 75mm gun (in the Sherman), a gun that the US viewed as relatively innacurate compared to other US guns.

I view British APDS among anti-tank rounds in 1944 much as I view German jet engines among aircraft in 1943. It would be silly to argue that APDS was not the better technology in the long run. The question is at what point it became mature enough to be practical for combat forces.

Different nations had different standards on what was practical. US standards of gunnery required greater accuracy, and greater barrel life, than British standards. On the other hand, British assessments of the armor they would have to defeat with their guns were ahead of US assessments. So they might well have had a better appreciation of what problem needed solving.

Added on edit:
At first glance it might appear that the W/O accuracy testing results correlate closely to the Issigny test. 56.6% at 400yds in one cast, 24 out of 42 at 200 - 600yds in the other. But the correlation is actually not very good. The W/O testing was on a "standard target", which was only a fraction of the size of the Panther's frontal aspect of the Issigny test (if you've never seen one in person, Panthers are HUGE!). Either case indicates an accuracy problem by US Ordnance standards, but one should not conclude from the W/O test that you could only hit a Panther 50% of the time at 500yds.

Hi Mk1. I wasn't suggesting you were dissing the 17pdr, but that such commentary is common on a lot of threads with little support other than the Isigny test. What makes this such a frustrating subject is that on the one hand there is so much comment on how poor the British guns were and so much blind awe claiming the German guns were 'god mode' weapons. One site has the effective range of the 75mm L/70 at 10km! Numerous sites spout records of Panthers killing T34's at over 4000m (I believe it happened once).

So to recap my position/concerns/questions...

APCR was developed for the 6pdr, but dropped in favour of APDS in a matter of months. If APCR was a more accurate projectile but suffered the common fault of all APCR (rapid loss of velocity due to poor sectional density) I don't see why that would matter if you can't hit anything over 500m anyway (inside existing performance parameters for APCR). I think APDS worked for the 6pdr, but didn't scale up to the 17pdr as well as hoped (more on that later).

The major source of error in gun accuracy is range estimation. Running a ballistics program I wrote I got the following figures for a 50% first round hit against a 10' wide x 7' high target with the range not known (and a good gunner);
PaK40 850m (correlates to documented sources)
75mm L/70 1000m
US 76mm 850m (correlates to documented sources)
US 75mm M3 675m
17pdr (APCBC) 950m

Note that this assumes a common projectile both in shape and longitudinal balance, so this is far from perfect, but it is not too far from being accurate. The US M3 may seem a bit harsh, but it was the basis for the other calculations (along with the PaK40). It should be noted that the calculations are based on ballistic coefficient and initial velocity and so favours high velocity guns. This is not always accurate as longer barrels are subject to whip and twist. If this were not the case, naval guns would have been a lot longer in the barrel. This then means that the 17pdr and KwK42 figures may be too generous and the M3 figures too harsh.

This is a long winded way of saying that the crew is probably the major variable in gun accuracy. I did find some info regarding APDS accuracy though...

Investigations into the innacuracies of 17pdr APDS at Woolich Arsenal showed that it was not the muzzle brake interfering with sabot separation but that it was a combination of the depth of rifling and the fact that the rear driving band doesn't properly engage the rifling until the shot had travelled 2" down the barrel. Essentially almost the full propellant load was put onto the front band at firing, and this band could not fully engage the much deeper rifling of the 17pdr barrel. Further, the duralumin bands were prone to tearing under the load. The result was the round not being properly centred in the barrel during the internal ballistics phase (and also explains why there were bits of sabot left to foul the barrel). None of these issues apply to the 6pdr as the original sabot was designed for that gun and adapted for the 17pdr.

As to accuracy, the Woolich test gives a spread of 14' by 16' (range not given but looks like 1000yds. I assume the range was known as the test was for dispersion). All shots at the outer end of the spread had deep grooves from the rifling in one side of the sabot foot indicating eccentric position in the barrel. Shots that landed within 3" of the MPI show no such marks. (3" from aim point is not bad when the round worked!)

(This is all from one grainy page of a doc marked 'Appendix to proc. no. 2,773. No date is visible, but inference from other docs suggest sometime around Dec '44))

The only clue I have to potential accuracy problems with APDS in the 6pdr is to do with the sights. Comments that APDS regularly hit 2' above the aim point indicate the sights were not able to give the different ballistic profiles of the ammunition. If true, that is a major oversight seeing as it is a common feature in many sights of the time. At longer ranges, with range estimation issues, not having a reliable aiming point in your sights makes shooting an art rather than a science/method. Still, if it was really that consistent, aim for the road wheels rather than centre of mass... I have only encountered one first hand account of APDS use from a 6pdr and this was at short range (under 500yds) and they scored 3 hits out of 3 on a Tiger 1 gun mantlet.

More recent discussions on learned forums on the 17pdr APDS indicated that a contributing factor initially was the training of the gunners - the high velocity of the shell allowed for a direct line of sight hit at 1000m, whereas the earlier APCBC rounds had a slightly arched trajectory at those sort of ranges, and the gunsights were calibrated as such. No one told the gunners and they continued to "aim high" as it were when using APDS, when all they needed to do was aim straight at the target - hence lots of misses. Which correlates with the comments made above.
I do not believe the accuracy issues were as bad after mid 1944, but we have little data by 1945 as there weren't that many German tanks for gunners to use APDS on.

Regarding the 105mmL67 in the T-95, I have penetration figures of:
T32 APCBC: 16cm/500m/90*; 15cm/1250m/90*; 14cm/1750m/90*
T29E3 HVAP: 28cm/300/90*; 24cm/1000m/90*; 22cm/1500m/90*

which is a piss poor performance given the calibre and barrel length. Possibly suspect figures.

For the hypothetical 120mm fitted to the T-95, I would use the figures from the 120mm T53 gun, later developed into teh gun on the M103. It's HVAP round penetrating 44cm/1000m/90* would make it top of the school, and even able to penetrate Maus, E-100 and the Krokodile.

A question I would have to ask opinion on, for WM47 scenarios, would American tanks have all HVAP loads, or mostly APCBC with a limited amount of HVAP like in WW2. Or put the other way round, would you consider it fair for game balance for everyone to have full loads of HVAP/APCR/APDS as appropriate?

Mark

More recent discussions on learned forums on the 17pdr APDS indicated that a contributing factor initially was the training of the gunners - the high velocity of the shell allowed for a direct line of sight hit at 1000m, whereas the earlier APCBC rounds had a slightly arched trajectory at those sort of ranges, and the gunsights were calibrated as such. No one told the gunners and they continued to "aim high" as it were when using APDS, when all they needed to do was aim straight at the target - hence lots of misses. Which correlates with the comments made above.
I do not believe the accuracy issues were as bad after mid 1944, but we have little data by 1945 as there weren't that many German tanks for gunners to use APDS on.

Regarding the 105mmL67 in the T-95, I have penetration figures of:
T32 APCBC: 16cm/500m/90*; 15cm/1250m/90*; 14cm/1750m/90*
T29E3 HVAP: 28cm/300/90*; 24cm/1000m/90*; 22cm/1500m/90*

which is a piss poor performance given the calibre and barrel length. Possibly suspect figures.

For the hypothetical 120mm fitted to the T-95, I would use the figures from the 120mm T53 gun, later developed into teh gun on the M103. It's HVAP round penetrating 44cm/1000m/90* would make it top of the school, and even able to penetrate Maus, E-100 and the Krokodile.

A question I would have to ask opinion on, for WM47 scenarios, would American tanks have all HVAP loads, or mostly APCBC with a limited amount of HVAP like in WW2. Or put the other way round, would you consider it fair for game balance for everyone to have full loads of HVAP/APCR/APDS as appropriate?

Mark

sultanbev wrote:More recent discussions on learned forums on the 17pdr APDS ...

I have observed several such discussions over the years. I only wish I had kept records of all the very good technical details that had been provided.

... a contributing factor initially was the training of the gunners - the high velocity of the shell allowed for a direct line of sight hit at 1000m, whereas the earlier APCBC rounds had a slightly arched trajectory at those sort of ranges, and the gunsights were calibrated as such.

This was pretty well understood within the testing circles by mid-1944. Piersyf's comments on the 2 foot high hits indicates this. Also the US pre-D-day testing of the 6pdr APDS concluded that the results should be rejected, and experienced British gunners used for any future testing, a clear indication that they felt that it took some ammo-specific knowledge to shoot APDS well.

I do not believe the accuracy issues were as bad after mid 1944, but we have little data by 1945 as there weren't that many German tanks for gunners to use APDS on.

US Army Ordnance felt the accuracy issues were still present through the early- to mid- 1950s. Otherwise they would have adopted APDS for the US 90mm and 120mm guns. Instead, they stayed with HVAP.

It was not for lack of development on sabotted projectiles. They had several. But they found many challenges in reducing the dispersion to US Ordnance acceptable limits.

It might be worth highlighting that dispersion is only one factor in combat accuracy. As Piersyf correctly points out, range estimation is also a key factor in combat accuracy. If the gunner mis-estimates the range to the target by a couple hundred yards (easily done at combat ranges) his round will either fall short, or fly over the target.

On this issue APDS had an advantage at range over HVAP. Both were very high velocity rounds. The faster you get to the target, the less time your round has to fall below it's point-of-aim. But APDS retained its velocity better, so that it was still going very fast at 1,000 yds and beyond. HVAP rounds slowed, making range estimation more critical at longer ranges.

But dispersion is also a key factor. If you shoot with APDS, and you are only 2 feet off due to range estimation error, but the round flies 14 feet off from your point of aim due to dispersion, you are not better off than shooting HVAP, where you might be 6 feet off due to range estimation error, but you are firing a round that has proven dispersion of less than 4 feet of your point-of-aim.

In combat the combination of less range-estimation error but more dispersion probably balanced out at WW2 combat ranges when compared with HVAP. That's why I believe that British gunners were not critical of the accuracy of early APDS.

But US Ordnance wasn't spec'ing nor testing combat performance. Ordnance saw their job as giving rounds that would fly true, and leave it to the gunners to figure out the range.

But that said, the problems with early APDS were many. The seperation of petal sabots (vs. pot sabots). The effect of muzzle brakes, both for possible impacts on the petals, and for ballistic perturbances even if their was no impact (note that 20pdr, 105s, and 120s have all dropped the muzzle brake?). The proper calibration of the gunsights for this new ammunition.

But also, more pernicious, is that APDS gets its armor penetration advantage not only from its high velocity, but from its cross-sectional density. The actual penetrator is longer relative to its diameter (higher L/D ratio), and heavier relative to both its length and its diameter, than full-bore AP rounds.

It is quite simply not possible to rifle a barrel such that it will fire 76mm diameter relatively low density / low L/D projectiles with the same stability as 40mm high density / high L/D projectiles. You need to choose what spin you are going to put on the round, and you need to optimize for one vs. the other. 6pdr and 17pdrs had their rifling spin rates optimized for full-bore ammunition (their primary service rounds), not for sub-caliber penetrators. APDS projectiles were less stable in flight as a result. They could not be otherwise. Fix the sabot seperation issues, fix the gunner's sights, fix whatever else you wanted to fix, but until you developed a gun that was specifically optimized to fire sub-caliber penetrators you could always achieve better test accuracy with HVAP than you could with APDS.

A question I would have to ask opinion on, for WM47 scenarios, would American tanks have all HVAP loads, or mostly APCBC with a limited amount of HVAP like in WW2. Or put the other way round, would you consider it fair for game balance for everyone to have full loads of HVAP/APCR/APDS as appropriate?

During WW2 US HVAP was not just limited -- it was almost unheard-of. Until perhaps February of March of 1945 the quantities were so small as to be almost irrelevant. (Also the first US HVAP rounds were poor performers. It took a redesign in the fall of 1944 to bring their real-world penetration up anything like their expected performance.

By Korea the US Army saw HVAP as a common item in load-out. It was typically issued at levels almost matched to full bore AP rounds, and was used in almost every tank vs tank engagement.

Don't know when the transition really occured (immediately post WW2, or as Korean combat ramped up, or somewhere in-between?). But metrics of the performance of both US Shermans and Pershings vs. Soviet-made T-34s in Korea primarily involve US HVAP ammunition.

Or so I am told.

If I were commander of a T-95 and had my choice of ammo loadout, I would have about 70% high explosive and semi-armor piercing high explosive (considering that most of my work would be bunker busting rather than tank hunting), 25% armor piercing shot, and 5% APDS (for those rare occasions when I come face-to-face with a Krokodil; unload the gun through the muzzle and jam in an APDS as fast as the loader can manage).

Don S.