Re-Examination of Russian APCR Penetration

[rexford]

Gathering up as much info as was available and making adjustments to trajectory model for arrowhead APCR yields following penetration figures, based on a DeMarre estimate from U.S. 76mm HVAP (247mm penetration with 38.1mm core diameter, 1.76 kg core weight and 1037 m/s muzzle velocity):

===================================

57mm APCR

24.13mm tungsten core diameter, 0.51 kg core weight. 1200 m/s muzzle velocity,

Penetration estimate might be reduced below following figures due to material ahead of nose which acts as armor piercing cap (and windscreen):

000m, 205mm penetration of rolled homogeneous armor plate

050m, 200mm

100m, 195mm

150m, 190mm

200m, 185mm

250m, 180mm

500m, 158mm

750m, 138mm

1000m, 120mm

Russian figures show 190mm at 100m, 145mm at 500m and 105mm at 1000m, about 15mm lower than DeMarre estimates. If the Russian figures are extrapolated to 0m the result is 206mm (76mm HVAP based estimate for 0m is 205mm).

==================================

76.2mm APCR

27.94mm tungsten core diameter, 0.48 kg core weight. 965 m/s muzzle velocity,

Nose of tungsten core is not shielded by solid material used as a cap.

000m, 123mm penetration of rolled homogeneous armor plate

050m, 119mm

100m, 116mm

150m, 112mm

200m, 109mm

250m, 105mm

500m, 090mm

750m, 076mm

1000m, 063mm

Above figures consistent with Russian data, 92mm at 500m and 62mm at 1000m.

=================================

85mm APCR

27.51mm tungsten core diameter, 0.64 kg core weight. 1050 m/s muzzle velocity,

Penetration estimate might be reduced below following figures due to material ahead of nose which acts as armor piercing cap (and windscreen):

000m, 173mm penetration of rolled homogeneous armor plate

050m, 170mm

100m, 166mm

150m, 163mm

200m, 160mm

250m, 157mm

500m, 142mm

750m, 128mm

1000m, 115mm

Russian figures show 140mm at 500m and 118mm at 1000m.

===============================

DeMarre estimates from U.S. 76mm HVAP are close to Russian firing test figures for 76.2mm and 85mm APCR.

Size of tungsten cores is unusual, 76.2mm and 85mm APCR have about the same diameter core, and 57mm APCR core is heavier than 76.2mm core although the 57mm core is smaller in diameter.

Would appreciate following information on 45mm APCR, tungsten core diameter and weight

nose length in terms of projectile diameter (a drawing would be best).

Thank you.

Velocities used in DeMarre equation derived from trajectory computer program prepared by Bill Jurens and Nathan Okun. Information on program inputs will be furnished upon request.

Data on Russian APCR projectiles and cores taken from Yahoo!Tankers files, particulars available upon request.

The above figures for 76.2mm and 85mm APCR are lower than what the game uses.

Net Surfer Bird

[rexford]

If the Russian figures at 100m, 500m and 1000m for 57mm APCR are extrapolated, the estimates become:

0m, 206mm

50m, 199mm

100m, 192mm

150m, 185mm

200m, 179mm

250m, 172mm

500m, 145mm

750m, 121mm

1000m, 102mm

The tungsten core round fired by 57mm L73 guns can sure defeat thick armor, being able to take on the Tiger frontally at 500m and piere just about any armor area. And the round should have lots of energy left once it gets inside a panzer.

On the other hand, the 57mm tungsten core is less than an inch across, and tungsten rounds had a tendency to shatter on hits with any kind of angle.

[flamingknives]

Interesting stuff.

[Soddball]

How would you extrapolate that to CM:BB? Is it that the tungsten rounds would produce a great many "penetration - no serious damage" results, rather than knocking the tank out. I assume you'd also see an increased ricochet frequency for 'curved' armour?

[rexford]

Originally posted by Soddball:

How would you extrapolate that to CM:BB? Is it that the tungsten rounds would produce a great many "penetration - no serious damage" results, rather than knocking the tank out. I assume you'd also see an increased ricochet frequency for 'curved' armour?

Go to following site for some neat stuff about 45mm APCR:

http://www.geocities.com/Pentagon/Base/1852/57mm.html#24

45mm APCR round contained solid mercury compounds that were converted to a toxic gas upon penetration. Bad for crew of penetrated panzer.

I don't know if 57mm, 76.2mm and 85mm APCR contained that mercury mix, but the small core in a 45mm APCR projectile would become quite lethal if it released toxic flumes.

Also be sure to note existence of 45mm cannister rounds. Following site notes that 45mm gun was used with great effect against infantry in Korea, which may be due to cannister(?):

http://www.rt66.com/~korteng/SmallArms/rok5.htm

[li]

In Korea, the antitank gun 45mm fired a very slow HE shell. These were slow but accurate. That si what the website must be refering to.

If the HE shell was slow, maybe it was a large warhead (maore HE type)?

[CavalryMan]

.. thank (insert deity here) there are people who do and are willing to share and develop our game in this way.

[Edited] because on re-reading I do get the concept if not the algorithms being mentioned.

What other board would include a summary of a technical thesis as a post.

[ March 28, 2003, 07:53 PM: Message edited by: CavalryMan ]

[rexford]

An American report entitled REVIEW OF SOVIET ORDNANCE METALLURGY, by A. Hurlich and dated April 1953, provides data on the diameter and weight of the 45mm APCR round and tungsten core.

The 45mm tungsten core weighed 0.25 kg and was 18.7mm in diameter, the entire projectile weighted 0.85 kg.

Based on muzzle velocities of 970 m/s and 1070 m/s for 45mm APCR, use of a trajectory computer program by Jurens and Okun, and a DeMarre penetration estimate from U.S. 76mm HVAP, the following penetration estimates were prepared for 45mm APCR against medium hardness rolled homogeneous armor:

45mm APCR from 45mm L46 gun

===========================

000m, 120mm

050m, 116mm

100m, 113mm

150m, 109mm

200m, 106mm

250m, 102mm

500m, 86mm

750m, 73mm

45mm APCR from 45mm L66 gun

===========================

000m, 138mm

050m, 134mm

100m, 130mm

150m, 126mm

200m, 123mm

250m, 118mm

500m, 100mm

750m, 085mm

Official Russian firing test data predicts 75mm penetration for 45mm L46 APCR at 500m, which is quite a bit below the above estimates. There is a possibility that the tungsten cores in 45mm APCR may have been "inferior" to 57mm, 76.2mm and 85mm cores, or the core dimensions given in the report may have been for later post-WW II projectiles and a smaller less effective APCR was used in 45mm gun during WW II.

Since the Hurlich report shows that 45mm APCR did not differ much from the other Russian APCR cores in terms of chemical composition and nose hardness (86 Rockwell C), it would seem that a smaller WW II core may be responsible for reported penetration during WW II but this is speculation at this point.

The 45mm tungsten core is superior to the 76.2mm core in terms of penetrator density, or weight divided by core diameter cubed. 45mm density equals 0.25 kg/18.7mm cubed or 0.00003823, while the 76.2mm core is 0.48 kg/27.9mm cubed for 0.00002210. Since one of the terms in the DeMarre penetration equation equals the relative density raised to the 0.7143 power, the 45mm core density results in an 48% penetration advantage for 45mm APCR due to relative density.

The relative density advantage of 45mm APCR over 76.2mm APCR is offset by the smaller diameter core, which results in a penetration multiplier of (18.7/27.9) raised to the 1.07143 or 0.65.

The Russian penetration estimates for 45mm APCR fired from the T70 gun display some penetration losses with range that bring the figures into question:

45mm L46 APCR

=============

0500m, 75mm vertical penetration, 60mm at 30 degrees from vertical

1000m, 59mm vertical penetration, 54mm at 30 degrees from vertical

1500m, 54mm vertical penetration, 51mm at 30 degrees from vertical

If the round losses 16mm vertical penetration from 500m to 1000m, it should lose more than 5mm from 1000m to 1500m based on my velocity estimates. It appears that the Russians may have used questionable velocity-vs-range figures.

It appears that all WW II Russian APCR contained mercury compounds which would release toxic gases inside a vehicle after penetration.

[rexford]

Russian firing tests supposedly indicated the following results for 45mm, 57mm and 76.2mm APCR against Tiger II side armor (80mm at 25 degrees from vertical hull side);

"The Russian tactics for combating the Tiger II were found in the following pamphlet written by Lt. Col. J. D. Skrobow and Lt. Col. A. N.Bukirew on ?The German heavy tank "Tiger-B" (Koenigstiger) and How To Combat It?, translated by the 17 .Armee on 4 February 1945:

...

All of the anti-tank guns in the Red Army can penetrate every armor plate on the Tiger-B ____with the exception of the front plates____.

...

Firing trials have revealed that the side armor on the turret and superstructure of the Koenigstiger can be penetrated at ranges up to:

-0 meters by the 45 mm anti-tank gun (sub-caliber and AP)

-600 meter by the 57mm anti-tank gun (sub-caliber)

-400 meters by the 76 mm ZIS-3 anti-tank gun (sub caliber)"

If we apply a 1.23 slope multiplier for 25 degree slope against tungsten core ammo and multiply by the 80mm side hull armor on Tiger II (superstructure side), we obtain 98mm vertical resistance.

The 76mm HVAP based penetration estimates for 76.2mm APCR predict 96mm vertical penetration at 400m, which is close to the estimated resistance of the armor.

45mm APCR is predicted to penetrate 120mm at 0m in the DeMarre equation analysis, which looks high. If the 120mm DeMarre penetration estimate at 0m is multiplied by 75mm (Russian figure at 500m) divided by 86mm (DeMarre estimate at 500m), the result is 105mm which looks high unless smaller APCR has higher slope effects.

If the 57mm APCR penetration is assumed to take place with a 30 degree side angle, the estimatedarmor resistance is 142mm vertical while the HVAP based penetration estimate is 150mm and the Russian figure is 135mm.

The above analysis shows that there are problems with the 76mm HVAP based estimates for 45mm APCR penetration, and the 57mm APCR DeMarre estimates are not consistent with firing tests against Tiger II side armor.

[JasonC]

Sounds like the formula with the 1.07 exponent underestimates the importance of the shell diameter to plate thickness factor. If the exponent of that term were more like 1.5, I think you'd see a more realistic relationship between the small 45mm penetrator and the larger ones. 45mm HVAP outperforming 76mm HVAP by a factor of 1.25 is not plausible on its face.