THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Discussions on the vehicles used by the Axis forces. Hosted by Christian Ankerstjerne
whelm
Member
Posts: 38
Joined: 07 Feb 2014 19:30

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by whelm » 16 Mar 2018 13:47

critical mass wrote:The M62 APCBC-HE could not sustain such high velocities without shattering.
2966 fps and above for shatter for the 75mm M61, so the M62 should be fairly similar.

Richard Anderson
Member
Posts: 2514
Joined: 01 Jan 2016 21:21
Location: Bremerton, Washington

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Richard Anderson » 16 Mar 2018 17:31

whelm wrote:
critical mass wrote:The M62 APCBC-HE could not sustain such high velocities without shattering.
2966 fps and above for shatter for the 75mm M61, so the M62 should be fairly similar.
As late as 1947, U.S. Navy tests at Dahlgren Proving Grounds found 3” M62 APC split and broke up when impacting 3” homogeneous armor plate at 30°and 60°obliquity at velocities up to 2,900 feet per second. On examination, the projectiles exhibited variable hardness with soft spots at the nose, contributing to the failures. J. J. Glancey, Progress Report No. 1 on Development of High Velocity Armor-Piercing Projectiles, (Dahlgren, Va.: U.S. Naval Proving Ground, 1 November 1947), p. i.
"Is all this pretentious pseudo intellectual citing of sources REALLY necessary? It gets in the way of a good, spirited debate, destroys the cadence." POD, 6 October 2018

critical mass
Member
Posts: 506
Joined: 13 Jun 2017 14:53
Location: central Europe

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by critical mass » 16 Mar 2018 19:01

The report is relevant. As mentioned before, it convincingly shows that the M62 APCBC-HE could not negotiate very high impact velocities. Notice that the tests were done against a rather benign form of armor: Ductile, 255-256BHN US class B armor (Ni-Cr type, similar to Krupp Q420 in composition and heat treatment) plate, 3" thick at 30° and 45°.
2900fps was far above the limit velocity for penetration. Actual shatter and nose breakage occured against 3" / 30° occured like:

expected limit velocity (Ord. Sk.78841): 2420fps (127% Ord.Sk. 78841)
actual trial results:
2423fps ---incomplete perforation (plug started at back) - projectile split (unfit to burst)
2495fps ---incomplete perforation (bulge in back) - projectile split (unfit to burst)
2518fps ---complete penetration (ductile hole formation) - projectile cracked but effective bursting condition
2522fps ---complete penetration (ductile hole formation) -projectile broke up (unfit to burst)
2549fps ---complete penetration (ductile hole formation) -projectile broke up (unfit to burst)
2627fps ---incomplete perforation (bulge in back) - projectile split (unfit to burst)
2740fps ---complete penetration (ductile hole formation) -projectile broke up (unfit to burst)
2755fps ---incomplete perforation (ductile hole formation) - projectile split but effective bursting condition (nose shatter only)

Notice that serious projectile damage rendering the HE-cavity ineffective were recorded down to the lowest attempted velocity of 2423fps (738.5m/s). Despite the projectile shatter and break up, the armor gave way in ductile mode, as intended. Harder plates increase the severity of projectile damage leading to shatter occuring at lower obliquities / lower velocities. This projectile was inferior to the US Navy Mk29 mod2 in these post ww2 tests. Actually it is interesting because the M62 Army APCBC copied the Navy sheath hardening pattern but was inferior to the Navy APCBC version. German wartime (1941/42) tests showed that the sheath hardening pattern will decrease penetration for calibres smaller than 105mm and decremental hardening patterns are superior by offering more high hardness support under the nose, inhibiting offset plastic deformation ( projectile nose bending away from target).

Against 45° declined plate, 3" was completely immune (no hole through) to M62 impacts due to complete shatter at the highest velocities, and break up at lower causing all projectiles to fail against the target (all projectiles broke up).
Increasing the muzzle velocity of the 3" gun would thus significantly increase the probability of shatter actually degrading battlefield perforation because it expands close range shatter issues towards mid range realms. This might reduce 3" armor penetration performance opposite to expectations.
With the given AP-quality it´s a wiser choice to move up in calibre and keep the same velocities.

Yoozername
Member
Posts: 1918
Joined: 25 Apr 2006 15:58
Location: Colorado

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Yoozername » 17 Mar 2018 16:19

I suppose that using the actual 17 pdr. projectile in the 3 inch would be another dead end since its increased weight over the M62 would negate the increased velocity.

The US should have been in possession of samples of the German Pzgr 7.62 cm used in the captured Soviet weapons circa 1943. If they did a comparison, or even firing trials with this from the 3 inch gun, they might have learned something.

seppw
Member
Posts: 99
Joined: 24 Dec 2017 00:49
Location: Central Europe

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by seppw » 17 Mar 2018 19:00

Yoozername wrote:I suppose that using the actual 17 pdr. projectile in the 3 inch would be another dead end since its increased weight over the M62 would negate the increased velocity.

The US should have been in possession of samples of the German Pzgr 7.62 cm used in the captured Soviet weapons circa 1943. If they did a comparison, or even firing trials with this from the 3 inch gun, they might have learned something.
Sorry for derailing, but how did the German 7.62cm ammo perform compared to the Russian one?

whelm
Member
Posts: 38
Joined: 07 Feb 2014 19:30

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by whelm » 17 Mar 2018 20:17

Yoozername wrote:I suppose that using the actual 17 pdr. projectile in the 3 inch would be another dead end since its increased weight over the M62 would negate the increased velocity.

The US should have been in possession of samples of the German Pzgr 7.62 cm used in the captured Soviet weapons circa 1943. If they did a comparison, or even firing trials with this from the 3 inch gun, they might have learned something.
Using a 17 pdr round in the 3" with some extra propellant could have improved some things.

They did comparison firings of German 88 vs 90mm and 75 vs 75 mm in 1944-1945, the conclusion:

"It is recommend that the design features, hardness pattern and composition of the German armor piercing projecticles be studied for the purpose of improving American armor piercing ammunition."

The trouble is when the US improved a round it's often still using the same nomenclature, so a 1942 M62 round will perform quite different from say a 1945 one, or a 1950 one and so on.

critical mass
Member
Posts: 506
Joined: 13 Jun 2017 14:53
Location: central Europe

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by critical mass » 17 Mar 2018 20:39

seppw wrote:
Yoozername wrote:I suppose that using the actual 17 pdr. projectile in the 3 inch would be another dead end since its increased weight over the M62 would negate the increased velocity.

The US should have been in possession of samples of the German Pzgr 7.62 cm used in the captured Soviet weapons circa 1943. If they did a comparison, or even firing trials with this from the 3 inch gun, they might have learned something.
Sorry for derailing, but how did the German 7.62cm ammo perform compared to the Russian one?
Captured soviet BR-350 APBC ammunition was the reason they had to issue new AP. When tested, they didn´t understood how one could issue these projectiles. Against a discriminate target, they penetrated only broken up at elevated velocities but german specifications rquired intact penetration fit to burst. Using the standart test criterium for 75mm Pzgr Gg rot acceptance (60mm @30°), these projectiles failed (plate not holed, projectiles mushroomed against the plate). The gun itselfe was valued as powerful but not the ammunition. It was noticed that the flat projectile nose caused to perforate almost exclusively by plugging, which would have been a desirable lower energy failure mode but in no case was the projectile strong enough to stay intact unless the plate was considerably thinner than cal. However, no conclusions were drawn a it was felt that they tested only inferior lots. When the Tiger manual was issued, they seem to have used the penetration data for the re-engeneered 7.62cm Pzgr 39 rot instead (vulnerable 800m-1000m front, and 1500m at sides).
During 1942 and 1943 they investigated the feasability of flat headed shots protected by a cap. These were found to be superior to Pzgr39 at medium obliquity but unlike them would break up against very thick (>2 cal) armor plate. They also later issued an APSH type projectile with soft core (HVAPBC-shot, Pzgr 40W) which had the ballistics of the Pzgr40 hard cored ammunition but a vastly different penetration mode: the windscreen collapsed, the soft, ductile iron core mushroomed out against the plate (rarely making a ricochet possible) and transferring some energy to induce spall from the backside of plate. Only feasable with very hard, brittle plates such as HHA 8S and 71-L when the impacted plate is smaller than the calibre.

Yoozername
Member
Posts: 1918
Joined: 25 Apr 2006 15:58
Location: Colorado

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Yoozername » 17 Mar 2018 22:16

seppw wrote:
Yoozername wrote:I suppose that using the actual 17 pdr. projectile in the 3 inch would be another dead end since its increased weight over the M62 would negate the increased velocity.

The US should have been in possession of samples of the German Pzgr 7.62 cm used in the captured Soviet weapons circa 1943. If they did a comparison, or even firing trials with this from the 3 inch gun, they might have learned something.
Sorry for derailing, but how did the German 7.62cm ammo perform compared to the Russian one?
It depends which gun was firing it! The Germans, as far as I recall, manufactured ammunition for the Soviet guns, that was a direct replacement for the Soviet ammunition using the 7,62 cm Pzgr 39 rot projectile. This could be used in any of the many Soviet weapons that could use it. This included most Soviet 76mm weapon except maybe the 76mm AA gun and IG. Then the Germans modified the Soviet F-22 guns to use the projectile on a Pak 40 cartridge. This was a rebuild and had better performance and actually became a German 'weapon'. There is evidence that the initial 740 M/s velocity was reduced in this weapon as the powder-weight seems to have been reduced. The Germans used these in Marders and field mounts and gave good service.

https://forum.axishistory.com/viewtopic ... zgr+39+rot

Also, there were many M62 manufacturers in the US with varying QC.


Richard Anderson
Member
Posts: 2514
Joined: 01 Jan 2016 21:21
Location: Bremerton, Washington

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Richard Anderson » 20 Mar 2018 16:23

Nick the Noodle wrote:Isigny Tests 12-30 JULY, 1944
Um, those are actually the findings of the Shoeburyness Test and the 1st and 2d Isigny Tests. There was also a test a Balleroy on 10 July.
One POV
Yes, I know what Nick's POV is, but how is it relevant?
"Is all this pretentious pseudo intellectual citing of sources REALLY necessary? It gets in the way of a good, spirited debate, destroys the cadence." POD, 6 October 2018

Nick the Noodle
Member
Posts: 53
Joined: 02 Mar 2018 20:49
Location: Land of the Dragon

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Nick the Noodle » 20 Mar 2018 16:51

Richard Anderson wrote:
Nick the Noodle wrote:Isigny Tests 12-30 JULY, 1944
Um, those are actually the findings of the Shoeburyness Test and the 1st and 2d Isigny Tests. There was also a test a Balleroy on 10 July.
One POV
Yes, I know what Nick's POV is, but how is it relevant?
I don't have a POV concerning the 76mm.

Isigny Tests are the 2nd and 3rd ones. Perhaps I should have titled it better.

The post was for info only.

seppw
Member
Posts: 99
Joined: 24 Dec 2017 00:49
Location: Central Europe

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by seppw » 21 Mar 2018 22:45

critical mass wrote:
seppw wrote:
Yoozername wrote:I suppose that using the actual 17 pdr. projectile in the 3 inch would be another dead end since its increased weight over the M62 would negate the increased velocity.

The US should have been in possession of samples of the German Pzgr 7.62 cm used in the captured Soviet weapons circa 1943. If they did a comparison, or even firing trials with this from the 3 inch gun, they might have learned something.
Sorry for derailing, but how did the German 7.62cm ammo perform compared to the Russian one?
Captured soviet BR-350 APBC ammunition was the reason they had to issue new AP. When tested, they didn´t understood how one could issue these projectiles. Against a discriminate target, they penetrated only broken up at elevated velocities but german specifications rquired intact penetration fit to burst. Using the standart test criterium for 75mm Pzgr Gg rot acceptance (60mm @30°), these projectiles failed (plate not holed, projectiles mushroomed against the plate). The gun itselfe was valued as powerful but not the ammunition. It was noticed that the flat projectile nose caused to perforate almost exclusively by plugging, which would have been a desirable lower energy failure mode but in no case was the projectile strong enough to stay intact unless the plate was considerably thinner than cal. However, no conclusions were drawn a it was felt that they tested only inferior lots. When the Tiger manual was issued, they seem to have used the penetration data for the re-engeneered 7.62cm Pzgr 39 rot instead (vulnerable 800m-1000m front, and 1500m at sides).
During 1942 and 1943 they investigated the feasability of flat headed shots protected by a cap. These were found to be superior to Pzgr39 at medium obliquity but unlike them would break up against very thick (>2 cal) armor plate. They also later issued an APSH type projectile with soft core (HVAPBC-shot, Pzgr 40W) which had the ballistics of the Pzgr40 hard cored ammunition but a vastly different penetration mode: the windscreen collapsed, the soft, ductile iron core mushroomed out against the plate (rarely making a ricochet possible) and transferring some energy to induce spall from the backside of plate. Only feasable with very hard, brittle plates such as HHA 8S and 71-L when the impacted plate is smaller than the calibre.
Hallo,
thanks for your infromative reply.
Image
I was told this was Russian 76mm. It's the side of a Tiger btw.

Yoozername
Member
Posts: 1918
Joined: 25 Apr 2006 15:58
Location: Colorado

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Yoozername » 21 Mar 2018 23:40

The Soviets actually had two loadings for this common ammunition. If the projectile had issues with the regular charge, the 'supercharge' would have been worse. The drawing seems to show both and is a guide to the two types. The Germans captured great quantities of not only the weapons but also the ammunition.

Image

German 7,62 cm Pzgr 39 rot. Note at 7.6 Kg it weighs 16.72 pounds. The US 3 inch was 6.8 Kg (M79) and 7 Kg (M62).

Image

Nick the Noodle
Member
Posts: 53
Joined: 02 Mar 2018 20:49
Location: Land of the Dragon

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Nick the Noodle » 22 Mar 2018 00:24

Yoozername wrote:The Soviets actually had two loadings for this common ammunition. If the projectile had issues with the regular charge, the 'supercharge' would have been worse. The drawing seems to show both and is a guide to the two types. The Germans captured great quantities of not only the weapons but also the ammunition.

Image

German 7,62 cm Pzgr 39 rot. Note at 7.6 Kg it weighs 16.72 pounds. The US 3 inch was 6.8 Kg (M79) and 7 Kg (M62).

Image
A better source of some German ammo here: https://www.ibiblio.org/hyperwar/USA/re ... German.pdf

Yoozername
Member
Posts: 1918
Joined: 25 Apr 2006 15:58
Location: Colorado

Re: THE 76 MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI TANK CAPABILITIES DURING WORLD WAR II

Post by Yoozername » 22 Mar 2018 01:31

I posted primary sources. Explain how the US data is 'better'? Do you know what a primary source is? Do you know what data is?

Return to “The Ron Klages Panzer & other vehicles Section”