I know the British considered this a serious enough issue that they went to replace the explosive filler and fuze in all APHE shells received from the US with inert filler and steel plugs. But what were the US specifications for fuse reliability in tank fired APHE shells? Where they expecting a near 100% burst behind the armour rate? 95%? 50%? And what was the maximum target obliquity/thickness/hardness their shells should've been able to pass through without damaging it's base fuse? In this 1944 test the premature detonation of the 90mm APHE projectile prevented it from defeating a target it otherwise should've been able to. This doesn't tell us much, besides that the M68A1 BDF was an inherently flawed design. The 76mm M62 projectile could not negotiate a 100mm/30° target in condition fit to burst. I have analyzed the firing results of the 75mm M61 inert loaded and fitted with a steel plug in place of the fuse and from 26 shots that perforated the armour, with the main body of the shell in one piece, only 4 times the shell failed to pass through in condition fit to burst, which still is 15% of total. This in only due to failure of the shell's body and steel plug itself. A live fuse would've doubtlessly added more possibilities of failure from premature or non-existant detonation. Does anyone have some information on this topic?
British testing of German APHE revealed very low reliability: The British considered the German employment of burster charges irrational, which is why they didn't employ them themselves.
Hi, Don Juan. Interesting document. Surprising results, as to my knowledge, the Germans considered the explosive effect behind the armour an important part of the overall performance of their APHE shells and dedicated considerable effort to ensure its reliable functioning. and Source: German service acceptance conditions for AP ammunition in ww2 - Axis History Forum Also, I'm attaching my translation of data from soviets testing German 37mm and 50mm guns against spaced armour combinations. Since we know that a 50mm solid AP shell fired at 835m/s, with or without a cap, would easily defeat a combibation of 20mm + 45mm of armour at 0°, it stands to reason that the german 50mm APHE shells start to reliably fail once the gap between two plates reaches 600-700mm is because their fuze reliably functions and detonated in mid air. Indeed, that's the conclusion reached by the authors of the original document: Source: The Russians test the Pak 38 and its PzGr 39 - Page 6 - Axis History Forum
Was the gun used a 5 cm KwK 38 L/42, which Pzgr 39 could penetrate 54 mm homogeneous armour plate at 30 deg from vertical? Maybe the explanation is that if the fuse didn’t work when the shell hit thicker plate, that didn’t matter much.
The general view of the British was that standard AP shot disintegrated on the inside of the armour sufficiently satisfactorily that a burster charge was extraneous, while also reducing the mass (and therefore penetrating effect) of the projectile and adding unnecessary sophistication to the manufacturing process. Middle East Forces were convinced that the explosive charge in German APHE rounds was very effective, and they requested British equivalents, but testing within the UK pointed to the opposite conclusion. The excerpt I posted was from a copy of an Ordnance Board proceeding that was typed up for Basil Liddell-Hart's records. I'll see if the proceeding number was noted, so next time I'm at Kew I might photograph the full proceeding itself.
Think it was a Pak 38 L/60, as a KwK 38 wouldn't have been worth testing, but I would need to source the original OB proceeding.
Yes, I am aware of the fundamental difference in the design principles of British and German A/T ammunition, and I think the British view is more logical, but there are always trade-offs. 5 cm KwK 38 L/42, which Pzgr 39 could penetrate 54 mm homogeneous armor plate at 30 deg from vertical from 100 meters/109 yds. At 500 meters, penetration was 46 mm. Re Peasant's 2nd message, German proof test was against 45 mm RHA at 30 deg, velocity: 540m/s. The muzzle velocity of KwK 38 was 685 m/s, so it seems that the gun used was KwK 38 and Germans were satisfied if the projectile kept its shape so well that it could explode after penetration, what happened when the projectile hit the armor plate which it could not to penetrate was not important to them. After I942 they clearly tested the 5 cm KwK 39 L/60 gun, but with a 10 mm thicker plate, the L/60 had a muzzle velocity of 835 m/s and could penetrate 57 mm RHA at 30 deg from 500 meters. But they accepted that the APHE didn't need to explode in extreme cases, they tested the lots against 55 mm plate vs 62 mm max penetration at the velocity used in the tests.
I think there is a bit of ambivalence about what the burster charge was for. In the field it was assumed that the explosive charge was itself intended to be lethal above and beyond its fragment scattering effect, although back in the UK the Ministry of Supply and Ordnance Board assumed that the burster was there as "insurance" in case the shell failed to fragment during the process of penetration.
Since the discussion has touched the armour penetration of the german 5cm gun, I'd like to share my current best estimates of it's performance: Estimated 50% perforation limit for intact projectile for 5cm Pzgr.39 against 300 BHN RHA at 30°: Spoiler: Spoiler Range (m) Striking Velocity(m/s) S.V.(fps) Armor Perforated (mm): 0 835 2740 84 50 821 2695 82 100 808 2650 80 150 794 2606 78 200 781 2563 76 250 768 2520 75 300 755 2478 73 350 743 2436 71 400 730 2395 69 450 718 2354 68 500 705 2314 66 550 693 2274 65 600 681 2235 63 650 669 2196 61 700 658 2157 60 750 646 2120 58 800 635 2082 57 850 623 2045 56 900 612 2009 54 950 601 1973 53 1000 590 1937 51 1050 580 1902 50 1100 569 1868 49 1150 559 1833 48 1200 549 1800 46 1250 538 1766 45 1300 528 1733 44 1350 518 1701 43 1400 509 1669 42 1450 499 1637 41 1500 490 1606 40 The german documents I've seen rate it's guaranteed penetration as 67mm/30° at 100m, so it's unlikely to reliably perforate armour thicknesses much greater than this, despite what this table shows.
On a slight tangent: I remember reading the Canadian digital archives and coming across a document describing testing of various designs of armoured ammunition bins for use in tanks. The interesting part is the authors selected an armour target of 40mm/30° in order to "... ensure an extensive and reliable breakup of the 2pdr AP shot". This part suggests that against some much less severe targets, British solid shot would remain whole after penetration and therefore likely overpenetrate the target. Might be something to keep in mind when assessing this gun's lethality against thinly armoured targets like halftracks or armoured cars. Edit: APHE design makes the most sense for low velocity guns that can defeat only up to ~1 caliber thick targets, as these, usually, do not provide enough resistance to break the shell into numeruors fragments on its own.
This issue manifested most clearly in the desert when attempting to deal with anti-tank guns, where 2 pdr AP would go straight through the gunshields without causing any damage. Middle East Forces lobbied for the original 2 pounder APHE shell to be reintroduced for this purpose, but the Director of Artillery at the Ministry of Supply would not have it.
If anybody wants a full copy of Ordnance Board Proceeding Q1834 on German 5 cm projectiles (as excerpted above), please PM me.
