HoHun, Tony Williams colleague explained that the spitfire and blenhiem tests were performed against multiple airframes and the pictures and films we see today are of the most dramatic results. The British did not understand how the Mineshell worked opposed to their HS20mm HE or HEI. In the Mineshell testing the results were that 30% of the airframes were kills and the rest unservicable.
The 20mm HE had a thick steel caseing which combined kinteic penetration due to the fuse timing then an explosion that threw around large slow chunks of the casing. I beleive the common explosive was 6-11 grams of TNT.
The 3 cm M-Gesch. 108 Ausf.A m. Zerl. had 85 grams of HA41 (hexogen aluminium) or 85 grams of penthrite. I've seen mostly HA41. The Stielhandgranate 24 stick grenade has 165 grams of TNT. HA41 is roughly 2.5x more energetic and explosivly burns 2x of TNT. TNT - 900c vs. HA41 - 1800c. The NS-37 HE had about 27 grams of TNT with a thick steel casing.
What the British did not understand about the Mineshell was the highly energetic explosion turned the thin steel caseing into tiny, sharp, very high speed shards that blew through aluminum skin, control cables, internal structures and crewmen like knives. The 8th Airforce performed tests on a B24 and determined the shell casing performed more damage than the explosion.
The Mineshell 30mm did not need to penetrate the aluminum skin due to the high speed steel shards. The photo of the B17 looks like the mineshell entered the open gunners window exploding inside which accounts for the amount of blast damage(85g HA41) and bulging. The Mineshell was being used since the BoB in Bf109E 20mm for the explosive shard damage effect against BoB British fighters. The germans used a collection of rounds in the 13mm-20mm knowing what the combined effects would be. Look in the back of Schiessfibel for a visual explanation.
The 3 cm M-Gesch. 108 Ausf.A m. Zerl. going off against the tail, body and wings of aircraft should be slicing up important structures underneath the aluminum skin. The least of which shreading oil lines, fuel lines and cutting control cables. Even wounding or killing the pilot and crew. If it happens to penetrate the skin before detonation, it should go off like a stick grenade pushed into the aluminum skin then the pin pulled. From reading, the sense I get about HE type fuses in general is explosion was at contact or there was just enough delay for the round to force into the aluminum skin allowing the detonation to expand into the ariframe cavety. Granted angle of attack to the aluminum surface could cause a bounce away or surface explosion relying on the casing shards to perform damage. HEI and SemiAP HE will have a delayed detonation fuze to allow full penetration and not used in the same rational as a Mineshell round.