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
Richard Anderson
Member
Posts: 2519
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 Apr 2018 16:09

Yoozername wrote:Both the M62 and M82 designs should perform better against FHA, but did the US really have 5 inch FHA sitting at 2500 yards away from the 90mm during a test? I suppose that almost all tank armor by the later years in WWII was homogenous? Actually, castings were being used for thicker armor?

If that data is 'true', then the 76mm should have had no issues taking on Tiger Is at 1000-1500 yards?
The language in Volume II of Terminal Ballistics is revealing. The data for vulnerability of German Panzers was derived by firing at various ranges at actual tank targets and was originally published in pamphlet form on 15 March 1944. However, it covered only Panzer III, IV, and VI (Tiger I). It is also evident they were all tested to destruction, fired at numerous times by numerous different weapons and projectiles. Volume II was also published in August 1944, before the results of the Shoeburtness, Balleroy, and Isigny tests were widely disseminated (or believed) in the U.S., but after the crash program for 76mm/3" HVAP and 90mm HVAP and T33 began. The 15 March 1944 data was eventually supplemented with the 90mm versus Panther pamphlet published 1 January 1945). All the penetration curves were superseded in Volume III (September 1945) from new firing data, but if you look at the charts, most of the actual firing was done at a limited number of range bands, armor thicknesses, and armor types for each projectile - the solid line intersections of the curves. All the rest - the dotted line intersections of the curves - were extrapolations.
"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

Yoozername
Member
Posts: 1919
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 Apr 2018 05:35

critical mass wrote:Notice that the data is a best fit curve for US trial data on US homogenious RHA armor. The latter is softer -in average- than contemporary german RHA and intends to always fail by ductile hole formation. While the effect of hardness difference itselfe is a rather mild one at 0° -30° obliquity when the projectile stays intact, one need to keep in mind that it will have a profound impact on the ability of the projectile to stay intact at elevated velocities (= short range), particularely if the projectile is of inferior quality such as M82 and M62. If the projectile breaks up, more of the energy usually expanded in ductile hole formation is spread out on the plate and this raises the critical velocity and consequently reduces penetration. Complete shatter will reduce penetration by approx. 1/3 compared to intact projectiles at normal impact obliquity.
I am fairly sure it was US armor. Always at the low end when people try to compare penetration graphs. The quest for a 'across the board' will allude this.

I hope to get time tomorrow to start a new discourse regarding the whole subject.

critical mass
Member
Posts: 508
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 » 22 Apr 2018 17:13

I don´t consider US RHA poor. It´s certainly the best material made by anyone during ww2 when You wanted a ductile plate behaviour with little to no spalling or plugging. It came at the disadvantage of marginally lower ballistic resistence and somehow lower abilities to damage projectiles and also required more alloying.

But it´s a material which is good against all types of attack, not just one (You remember that soviet MZ-2 was excellent if it breaks up the projectile but worse than mild steel if it fails to).

User avatar
Mobius
Member
Posts: 494
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

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

Post by Mobius » 23 Apr 2018 03:01

Richard Anderson wrote: Volume II of Terminal Ballistic - The 15 March 1944 data was eventually supplemented with the 90mm versus Panther pamphlet published 1 January 1945). All the penetration curves were superseded in Volume III (September 1945) from new firing data, but if you look at the charts, most of the actual firing was done at a limited number of range bands, armor thicknesses, and armor types for each projectile - the solid line intersections of the curves. All the rest - the dotted line intersections of the curves - were extrapolations.
The US data doesn't seem to have changed from 23 Sept. 1944 TM 9-1907 Ballistic Data to July 1948 TM 9-1907 Ballistic Data. The graphs are clearer but no ballistic differences.

critical mass
Member
Posts: 508
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 » 19 May 2018 19:16

Added is a graph synthesized from Lilienthalreport 166, dated 1943, p.109, Abb. 1 and -3, p.112, Abb.9-10 for mass production, german AP perforation performances. Performance related to tests conducted at 60° (90° = perpendicular to the plate). Definition of penetration is the usual, german consecutive 5/5, G(d), except for G(g), for conditions (dotted lines) where 5/5 consecutive is not possible anymore with INTACT projectiles due to projectile break up caused by the inferior, old series AP and APCBC projectiles.

-as an interesting observation, the KWK40 reliable projectile performance with 7.5cm Pzgr39 was better than the 8.8cm KWK36 reliable penetration performance with 9.5kg Pzgr Gg (Flak ammo), at least against the ~100kg/mm² strong, sort of mediumish hard, special test armor fired against in these trials. On the battlefield, the 8.8cm would likely be better against softer, 67-75kg/mm² / 225BHN RHA armor, due to a much delayed projectile break up (consequently shifting towards intact line for 8.8cm Pzgr39) and against very hard HHA armor, too, due to the adiabatic shear effect eased by larger cal. attack.

Notice the drop in tensile strength of the test plates correlated with increasing plate thickness (section thickness).
The unusual "curve" of the 5cm Pzgr Gg is correct. The curve flattens due to projectile break upof the uncapped projectile. However, the lack of a CAP improves performance compared to the capped 5cm Pzgr39, under conditions where both projectiles stay intact.
Shatter velocity are marked with arrows. I have added them as the mean from *very many* [N=1182] trial results conducted 1942. The old projectile drawings are not to a similar scale.

edit: added BHN aequivalent numbers next to kg/mm^2 scale. For the reliability of the penetration curves, which were created from empirical prooving ground testing -not by calculation- with good quality*, mass produced projectiles (in Fertigung befindliche Geschosse) one might refer to the originally classified SECRET article by J. Sitz in the Lilienthalpapers. Particularely to
"Die angegebenen Werte sind durch Beschuß festgestellt und gelten für gute Geschosse. Es sind dieselben Werte, die in dem Heft "Durchschlagsleistung der Panzerabwehrwaffen" den anderen Diensstellen mitgeteilt und den mit WaPrüf 1 zusammenarbeitenden Firmen im Rahmen des monatlichen Erfahrungsaustausches bekanntgegeben wurden." -p.110, emphasized by myselfe
.

*good quality refers to a lot of known, good quality from mass produced projectile lots. Germany did not produce special proof shell during ww2. Projectiles from those lots were selected, which passed their respective service proof trials without having one projectile undergoing any form of change of shape (2 out of 2 success, rather than 2 out of 3. Latter lots, where one single failure occured were not used for these trials).


hope it helps,
Comments welcome.
You do not have the required permissions to view the files attached to this post.

User avatar
Mobius
Member
Posts: 494
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

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

Post by Mobius » 18 Jun 2018 01:20

The 76mm HVAP was highly accurate. Though it seems that the mount made somewhat of a difference. Firing from the light M18 Hellcat seemed not as accurate as the M10 tank destroyer. In both cases these guns had the 1:40 rifling twist. But the difference might be gun jump. (From N-5590.14)
Contrary to what it says in Wiki the 76mm M1A1C also retained the 1:40 rifling. Only the 76mm M1A2 had 1:32 rifling.
You do not have the required permissions to view the files attached to this post.

Yoozername
Member
Posts: 1919
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 » 18 Jun 2018 16:38

Interesting, I think that may be the first data I have seen regarding that round's accuracy. Much anecdotal information, but to have a 1 meter vertical dispersion at that range is remarkable.

The penetration data shows the fall-off the HVAP experiences from as little slope differential as going from 20 to 30 degrees. Compared to M62.

User avatar
Mobius
Member
Posts: 494
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

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

Post by Mobius » 19 Jun 2018 01:10

The sights on the guns sometimes had to make allowances for the jump and ballistics.
76mmHVAPsight1.jpg
76mmHVAPsight2.jpg
You do not have the required permissions to view the files attached to this post.

User avatar
Mobius
Member
Posts: 494
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

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

Post by Mobius » 23 Jun 2018 17:42

Here's the gun jump on those guns. I couldn't come up with a pattern here other than the M10 has less jump than the M18. But the M4 has more jump in the M1A1 than either.
Another thing the "to use chart" instructions above are wrong in several charts when comparing to bore sight ranges. They don't apply in all cases.
You do not have the required permissions to view the files attached to this post.

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