8,8 cm PzGr 39 Performance

[Miles Krogfus]

Using the Krupp May 2,1944 4AKB 9524 chart of perforation curves for Krupp Projectiles, and the German Firing Table for 8.8 cm Pzgr 39 FES (39-1 and 39 Al) weight 10 kg, yields these 30 degrees of deflection figures for PzGr 39 (as used by the the Tiger I) 100 meters 770 m/s 123 mm of HB 275-302 plate, 500 meters 734 m/s 113 mm same HB plate, 1000 meters 690 m/s 102 mm same HB, 1500 meters 647 m/s 92 mm also HB 275-302 plate, 2000 meters 607 m/s 84 mm HB 302-329 plate.
A Russian Chart show this projectile's 30 degree deflection perforations as: 100 m 98 mm, 500 m 91 mm, 1000 m 84 mm, 1500 m 78 mm, 2000 m 72 mm. American tests of 39 PzGr 39 (and PzGr 39/43 used by the Tiger II) showed that they had a higher carbon content, and thus more hardness and armor plate perforation per caliber than Russian projectiles. At the start of WW II, Russian AP had a specified hardness of at least 45 RC (HB 421). Late war 85 to 122 mm AP reached at most 50 RC (HB 481). For example, the 122 mm BR 471 had a 35KH3NM analysis of C .29-.38, Si .22-.36, Mn .32-.58, S and P .02, N 1.0-1.3, Mo .2 and Cr 2.69-2.85. PzGr 39 tested in America had C .52-.59, hardness up to 60 RC (HB 654).
The Russians used the DeMarre formula, normally with a K factor (projectile/plate coefficient) of 2400 to estimate AP performance, and when they applied it to German guns, got their own results. Russian AP that were produced from the late 1930's to the 1950's had the same range of carbon and hardness. WW II British AP had the most carbon (Panzers watched out for Fireflies in Normandy). Also, only after the war did errors in Russian tank gun and artillery firing tables get corrected. WW II Russian firing tests versus German armor plate at an actual 100 m, with AP speeds adjusted for their official m/s at other ranges, gave the wrong distances such AP as the 122 mm BR 471 would actually pierce Panzer plate. Note that the capped version of 122 mm AP was not used in the war, only uncapped BR 471 was fired.

[Miles Krogfus]

The perforation figures I have given are for the 10.2 Kg projectile. Here are the mm penetrated for the basic 10 Kg Tiger I projectile: 100 meters 118 mm, 500 m 109 mm, 1000 m 99 mm, 1500 m 90 mm and 2000 m 81 mm. 88 PzGr 39 made by its sub contractors could perforate the same mm of plate with a 4 to 10% increase in velocity. The Krupp figures are for its best projectiles checked at the Krupp factory firing range.

[Yoozername]

These are all monobloc?

[Miles Krogfus]

Munitionsmerkblatt 5 dated December 12,1943 gives these perforation figures for the Tiger I's 8.8 cm Pzgr.Patr. 39 KwK 36, weight 10.2 Kg, muzzle velocity 773 m/s, 30 degrees deflection:
at 100 meters 120 mm, 500 m 110 mm, 1000 m 100 mm, 500 m 91 mm, 2000 m 84mm. These are the "official" OKW figures. The Tiger's firing table has a MV of 780 m/s.

[Yoozername]

Looks like a monobloc here

[Miles Krogfus]

Thanks for the drawing image, it caused me to find Zeichnung Nr 13C1310 of the monobloc PzGr. 39/43 and realize my careless mistake! PzGr 88 never was made in a welded version like Panther 75 mm APBC . . .

[Yoozername]

The Germans gave up on the welding AP as it introduced much expense and manufacturing delay. And, in the end, was found to be unnecessary. I have seen earlier 5,0 cm PzGr that were welded as well. By the time the larger 88mm AP was manufactured, it was gone.

The Panther ammunition was manufactured in decent quantities long before the summer of 43, and given the teething problems and losses of Panther, I imagine they may have had stocks till the Panther fleet had built up numbers. Not so for the PAK 40 and KWK 40 weapons. They were responsible for a large part of tank kills in 1943 and they could not wait around for a slow ammunition manufacturing process that was not really needed.

[Yoozername]

I believe this is the chart?

[Miles Krogfus]

These Russian figures shows how much German PzGr. rounds WOULD penetrate with the the same DeMarre projectile/armor plate relationship (K) that Russian projectiles had. But PzGr. did not have this K . . . Russian projectile experts failed to realize this.
In 1943 the 85,100 and 122 mm rounds prepared for use against the "New" Panzers were given K 2400 on their "official" firing tables. For example, a statement in the first SU 85 firing table FT #240 gave crew members its APBC's supposed penetration, and states these figures are obtained using a DeMarre K 2400. Anti-Tank rounds the SU was using: BR 365 APBC and BR 365K AP. MV 792 m/s fired by D5-S 85, D5-T 85A, Type 1943 D 5-T 85, and type 1944 ZIS-S 53.
Here are the 0 degrees and 30 degrees deflection figures: 100m 119/97mm, 250 m 114/94, 500 m 111/91, 750 m 107/87, 1000m 102/83, 1500 m 93/76, 2000 m 85/69, 2500 m 77/63, 3000 m 70/57 mm.
In a bit, I will post "biographies" of WW II Russian projectiles from primary data I have from the 1930's through the !960's.

[Yoozername]

I think most people take that chart with a sack of salt...

I would welcome primary sources. It's amazing how secondary sources are re-quoted till they become the defacto-internet truth.

[Yoozername]

Actually, that chart seems to show the early 88mm 'flak' round. Still, there are questions...what armor is it supposed to penetrate, etc.?

I really hate when penetration figures, from different countries, using different testing methods, different armor, etc. The typical comparisons and guesses can't be anything guesses.

[Miles Krogfus]

Yes, the German 88 MM m/v of 810 m/s second is wrong for the Tiger I's gun. I haven't used DeMarre to check the velocities of the Flak FT compared to what the formula would yield in relation to the chart's at range figures, since I do not not regard them as valid . . .

[critical mass]

88mm Pzgr39 (KWK43/PAK43) specified german performances:
60°off the perpendicular = 88mm RHA complete penetration (projectile broken) at 100m = 990m/s FT velocity, est. 72mm RHA at 900m/s, est. 81mm RHA at 950m/s
55° off the perpendicular est. 99mm RHA complete penetration (projectile broken) at 100m = 990m/s FT velocity
50° off the perpendicular = 113mm RHA complete penetration at 100m = 990m/s FT velocity
45° off perpendicular est. 130mm RHA complete penetration at 100m = 990m/s FT velocity, est. 93mm at 850m/s
40° off the perpendicular = 152mm RHA complete penetration at 100m = 990m/s FT velocity

88m Pzgr 39 performance in soviet firing tests vs IS3:

IS3 hull trials:
110mm soviet RHA glacis (pike, 59° obliquity): no complete penetration at 0° & 40° target angle, at 975m/s only cracks started at back plate
110mm soviet RHA nose plate: (nose plate, 55° obliquity): 971m/s complete penetration, 844m/s = no penetration (bulge but no crack at back plate)
90mm vertical side armor at 45° target angle: 877m/s complete penetration, 825m/s no penetration (cracks started at back plate)
90mm sloped side armor (screened by thin, spaced plating) at 60°: no complete penetration, cracks started at back plate surface with 980m/s

IS3 (prototype) turret trials:
90-100mm cast armor at 59.2° compound netto obliquity (composed of 58° vertical at 15° horizontal component) complete penetration at 900m/s.
90-100mm cast armor at 62.3° compound netto obliquity (composed of 58° vertical and 30° horizontal component) complete penetration at 965m/s.

IS3 turret cast armor. The turret tested was made from hardened cast armor. Cast armor can be expected to be significantly inferior at high oblique impact to RHA. In the 90mm to 100mm thickness range, cast armor was ca. 20% to 30% inferior to german RHA. In correspondenc eto these trials, the IS3 turret armor had to be considerably reinforced in armor thickness.

IS3 glacis plate of 110mm. Nothing significant can be gained from this test, however, starts of cracks at 971m/s indicate too britlle armor.

IS3 nose plate of 110mm. This armor plate shows inferior levels of ballistic resistence compared to german RHA in this thickness. Penetration at 971m/s shouldn´t be expected outside the 95mm-100mm range if it would be on par with german RHA. Apparently, this soviet IS3 RHA was at least between 10% and 16% inferior to german RHA under this high oblique impact. The large spread between complete penetration and protection likely should be viewed as an artefact of the testing, and indicates that the lower limit of ballistic performance have not been reached yet. Complete penetration of soviet 110mm RHA at 55° therefore occurs somewhere >844m/s but <971m/s.

IS3 Side armor of 90mm RHA: Behaved as good as german RHA in this thickness range. Also the 90mm RHA inclined upper side plate incdicates good quality, though this is less certain due to the possible effect of spaced plating in stripping off the AP-cap of the Pzgr39. The lower cast armor quality becomes tellingly apparent when one considers that the 90mm RHA upper side plate could not be penetrated at 980m/s by this projectile while the thicker, cast turret would be completely perforated at only 900m/s.
The level of ballistic resistence offered by the 90mm RHA upper side plating (+ spaced plating) on the other hand was on approximately the same level as the 110mm pike plate (in both cases, cracks at back surface started at 975 & 980 m/s but no complete penetration). This also points towards good quality 90mm RHA plating but ca. 10%-20% inferior ballistic resistence of the thicker, 110mm RHA plates.

88mm Pzgr 39 in US trials:

Tests conducted at 55° vs US RHA of 92mm thickness penetrated twice at 3334fps (1016m/s) in broken up condition and failed once to completely penetrate (hole through) at 3310fps (= 1009m/s). In all cases the projectile shattered

Tests conducted at 45° vs US RHA of 130mm thickness showed four failures due to shatter at velocities between 772m/s and 979m/s, causing twice holes and twice through cracks in the plate. A fifth projectile, fired at a velocity of 1002m/s penetrated completely, but with broken nose and base damage.

It´s possible -and in my opinion even probable- that the 88mm Pzgr39 projectiles used in US trials were passed before autumn 1944 and therefore were made according to the older 30° proof angle specification. Under the 30° tests, the 88mm Pzgr 39 rarely broke up in US trials and behaved superior.
The presumption that these 88mm Pzgr39 were not up to the latest specifications is supported by the fact that neither of the five projectiles passed the relatively soft 130mm armor plate at 45° in a condition fit to burst -whether they penetrated or not. However, intact penetration of 130mm german RHA was required in the revised service acceptance conditions 1944.
In a second series of trials at the US Army PG this was achieved even by the 75mm Pzgr39 ammunition, which penetrated 132mm US RHA at 45° with 962m/s & 996m/s, in both cases with the projectile intact through the plate (no break up or deformation). At velocities below 3099 fps (945m/s), the 75mm Pzgr 39 tested at the USAPG rejected off the plate but in three of four cases it rejected intact -again without break up, whether or not it penetrated.

Therefore, it´s really difficult to assess US armor quality from this trial alone. The good ballistic resistence of the softer US RHA seems to me more an artefact caused by insufficient 88mm Pzgr39 projectile strength of the lot of projectiles used in the trial rather than an attribute of superior reistence of the armor plate. Else, the 75mm Pzrg39 would have to be reviewed as vastly superior to the 88mm Pzgr39 in oblique impact, an idea which,considering other availabe evidence, is not believed to be the case.

[critical mass]

I believe this is the chart?

Miles Krogfus interpretation on this table has turned out to be entriely correct. The penetration figures in this table are CALCULATED with De Marre K=2400 (Расчетная при K=2400).
they do not represent actual test data -at all- and in regard to german guns in particular, indicate only an estimate which would be right only in case had they fired the soviet inferior APHE/APBC-HE projectiles instead of the virtually indestructable Pzgr39.

I have added the missing front page to this memo to proof Krogfus´s argument. Notice that Peter Samsonov likely knew this front page when he posted the table and decided to outright lie about the charakter of the penetration data when asked about it, presenting them as if they were actual firign trial results...

[whelm]