U.S. Tests with Russian Flat Nose Ammo

[rexford]

The WW II Russians used anti-tank projectiles which were unlike those in use anywhere else due to their flat nose and relatively low hardness. The true performance of the rounds was somewhat masked by official wartime Russian penetration figures for their flat nose APBC rounds (BC indicates a wind screen), which were based on DeMarre estimates against cemented plate and found their way into German and British intelligence reports.

Much speculation has surrounded the performance of the flat nose Russian projectiles. British and American theory held that the flat nose would dig into sloped armor and counter ricochet forces, improving performance on angled hits. However, tests with 20mm projectiles and some full size 75mm versions suggested that the flat nose rounds had trouble defeating vertical or sloped armor thicknesses 10% greater than their diameter, due to nose shatter.

U.S. firing trials with 100mm and 122mm Russian flat nose APBC rounds offer a view into how those rounds actually work, which supports some theories and counters other concepts.

The 122mm APBC penetration curves cover angles from 0 through 70 degrees impact (rolled armor targets), and are based on Aberdeen Proving Grounds report DPS-647. At velocities from 2200 to 2600 fps, the vertical target penetration of the 122mm projectile increases as the velocity raised to the 2.5 power, and varies from 135mm to 206mm. The overall shape of the curve suggests that shatter did not occur.

Against 60mm plates at 60 degree slope from vertical, the 122mm APBC slope effect is 1.58 and the sloped armor resists like 95mm at vertical, less than the see through horizontal distance. The 122mm tests support the theory that flat noses boost sloped armor performance, and counter the theory that flat noses are prone to penetration robbing shatter against thick armor .

The 100mm APBC tests present some different results from the 122mm, and are based on APG report DPS-1661. From 2200 through 3000 fps, the tests against vertical cast armor relate vertical penetration to a near linear function of velocity (132mm at 2200 fps, 157mm at 2600). The smooth shape of the 0 degree curve suggests an absence of sudden shatter as thickness increases, but the reduced penetration increases may signal increasing projectile damage.

The sloped armor penetration of the 100mm APBC, at angles from 30 to 75 degrees, appears to be consistent with the 122mm APBC trials when cast armor is converted to rolled equivalent. This suggests that the 100mm round is suffering damage against vertical and near-vertical targets as thickness/veocity goes up, but is performing like the 122mm against sloped armor.

While the 100mm and 122mm APBC curves may be based on post-WW II ammo, they were used to predict the vertical penetration of WW II Russian flat nose ammo agianst rolled armor (cast thicknesses coverted to rolled equivalent). Comparison with WW II Russian trials resulted in some surprising results.

When 100mm APBC penetration was used to predict 57mm and 76.2mm APBC at 0 degrees, the following comparisons with WW II Russian tests were prepared:

57mm BR-271 APBC with 990 m/s muzzle velocity

100mm APBC based prediction: 104mm at 500m, 93mm at 1000m, 84mm at 1500m

Russian tests: 102mm at 500m, 95mm at 1000m, 84mm at 1500m

76.2mm BR-350B APBC with 2148 m/s muzzle velocity

100mm APBC based prediction: 87mm at 100m, 81mm at 500m, 74mm at 1000m, 67mm at 1500m

Russian tests: 90mm at 100m, 80mm at 500m, 73mm at 1000m, 66mm at 1500m

The 122mm APBC estimates for 57mm and 76.2mm APBC were not as good as the 100mm based predictions, and were up to 45% different from the 57mm test results.

Russian test data for 45mm, 85mm and 152mm APBC appears to be consistent with 122mm APBC based estimates, and the 100mm APBC based figures do not compare well for those rounds.

The above data and results suggest that Russian APBC may be prone to damage effects based on shape, since the 57mm, 76.2mm and 100mm APBC projectiles differ substantially from 122mm APBC and appear to follow different penetration equations at low angles. 76.2mm APBC has about 40% of diameter as flat nose while 122mm has about 20%, and the 57mm and 100mm APBC are relatively longer than the 122mm APBC for their width even though relative flat nose width is about the same.

The trials with 20mm and 75mm flat nose rounds that observed severe nose shatter were made with projectiles where the flat nose made up about 85% of total diameter, which supports the theory that shape may be a critical factor for flat nose projectile effectiveness.

While the 100mm and 122mm APBC results may be based on post-WW II ammunition, the curves appear to be consistent with WW II projectile performance.

[Spook]

Good to see that you're still holding sway with your armor/ballistics research, Lorrin.

I suspect, though, that subject matter like this is a bit dry for most CM gamers, unless the CM armor grogs are being told that some given ordnance projectile has a variation in penetration ability of 15-20% or even more.

So, along with the referencing documents, I do hope you've provided this to Battlefront via e-mail.

[rexford]

Originally posted by Spook:

Good to see that you're still holding sway with your armor/ballistics research, Lorrin.

I suspect, though, that subject matter like this is a bit dry for most CM gamers, unless the CM armor grogs are being told that some given ordnance projectile has a variation in penetration ability of 15-20% or even more.

So, along with the referencing documents, I do hope you've provided this to Battlefront via e-mail.

Thanks for response. Posted the whole article for those few (very few) who would be interested in little details.

My long post adds some credence to T34 76.2mm APBC penetration against Tiger side 82mm, suggests that armor could be defeated at just under 500m if gun is lined up to hit armor face to face.

Some Russian tanker anecdotes state that T34 could penetrate Tiger side armor at 500m, but that range was considered suicidal and it would seem that few T34 dared to approach that closely.

There are German maintenance and field reports where Tigers were hit many, many times by 76.2mm and 57mm Russian rounds without a single complete penetration. Tigers in these combats appear to have been surrounded.

Given the penetration data for 57mm and 76.2mm guns, where 57mm penetrates 102mm at 500m and over 90mm at 1000m, one might wonder how 57mm hits could land all over a Tiger and not penetrate.

At Kursk, 76.2mm rounds from ATG and tanks hit the side of a Ferdinand many times at 300-400 meters range before one round penetrated without much effect.

The above info suggests that while Russian APBC could penetrate 80mm test plate, something may have been happening in the field to reduce projectile effectiveness. Maybe the rounds were shattering when penetration was in excess of that needed for 50% success, or were not of the highest quality.

Some German documents suggest that T34 APBC rounds could not penetrate the Tiger side armor at 200m, based on Russian tests. German records for Tiger units usually indicate no 76.2mm penetrations.

Many folks have questioned 37mm ATG penetrations of the T34 turret front during 1941 and 1942 combat, I wonder if T34 defeat of Tiger armor strikes anyone as optimistic.

[Runyan99]

Bump, just for Rexford.

[Mark Gallear]

I was very interested.

[Andrew H.]

These little details are great; I think a lot of people are interested in them.

[K_Tiger]

Those Penetration datas are from firing trials in optimum conditions (for the firing round), if i can it say so.

In a real battle, you were seldom in the position for a sure point-blank shot. Even if the firer is in a 90° position, there is mostly a slight angle left, so i think it would be hard for both US/RU 75/76mm weapons to defeat the side armor from a Tiger.

Plus the really good steel quality, who im assume, it was better then the US/RU testing plates, but didnt we hade this discussion before??..

[jrcar]

Always of interest.

Cheers

Rob

[DevilDog]

Being an engineer I always find such technical information highly interesting, but am too lazy to look for it anywhere besides a Rexford thread.

Keep it coming.