Hi Karnak,
>I'm not talking about AP 20mm shells.
Oh, sorry for the misunderstanding then.
>I'm talking about the difference in an HE shell that explodes on, or near, the surface like the German Mine shells compared with an HE shell that explodes deeper in like the British Hispano HE rounds.
There mine shells had a delayed action fuze that made them blow up within the airframe. This was imperative to get the full blast effect - the shell has to explode in a confined space for the greatest destructiveness.
I think it were the Hispano HE rounds that had the fuzing problems leading to detonation on the surface, not the mine shells.
The greater penetration capability probably gave the Hispano some capability against "hard" components (though a 10 g charge won't blow off the main spar, anyway).
However, with only half the explosive content, it was less than half as effective as the mine shell in destroying the aircraft's load-bearing skin. During mine shell development, it had been recognized that it was essentional not just to blow sections of skin off the aircraft, but to make the damage jump the riveting of the attacked section to weaken the adjacent sections. In that way, a larger charge could do much heavier damage than a smaller charge as it destroyed the load-bearing properties of a much larger skin area. (In the end, this lead to the 30 mm mine shell, of course.)
To get back on the topic of the MG FF: While mine shells were most effective against an aircraft's wings, their effective target area wasn't limited to it. There's one interesting Battle of Britain era photograph that shows a Spitfire which took a single MG FF/M hit into the empty rear fuselage. The entire tail got "soft" and was bent to the point of wrinkling the aluminium skin. Though the pilot got the aircraft down safely (no doubt with great care to avoid any hard manoeuvres), the plane was beyond repair and had to be written off.
Regards,
Henning (HoHun)
