Hi scJazz
Thanks for your interest, What you say is true for the 30mm MK108 but less applicable to the early German 20mm cannon and not really relevant to the later war German 20m Cannon.
If you have a look at the tables in the reference I supplied above, here it is again for easy reference,
http://www.quarry.nildram.co.uk/WW2guneffect.htm
We can see in the first two tables that the hispano fired the 20x110 round with a muzzle velocity (MV) of 860/830 m/sec the MG 151/20 cannon fired the 20x82 round with a MV of 720/800 m/sec
However the German MG-FF and MG-FF/M fired the 20x80RB round with MV of 585/585/700 m/sec.
This site
http://www.bf109.com/armament.html
Gives the MG-FF(early war licence built oerliken see
http://en.wikipedia.org/wiki/MG_FF_cannon ) a MV of 600 as fired from the ME-109. MG-FF was replaced by the MG-FF/M beginning summer 1940 (Bf 109E-4 onward) firing the same round but with a better MV of 700 m/sec
Mind you the 257 gm weight of the Hispano round compares well with the german rounds 182 gm and 205 gm.
I dont know how the SPCAMO determines AP pen but the German guns and the Hispanos performaces dont look that dissimilar to me. Certainly all the numbers required are readily available in the references I mentioned.
It is correct that the thin walled Minengeschoss shells had poor AP performance but a very much larger payload of HE. See %HE content in
http://www.quarry.nildram.co.uk/WW2guneffect.htm
ie the Hispano is 8 % HE and the Minengeschoss is 22% ie the German shell has nearly three times the HE content of the Hispano shell.
This could be seem as justification for giving the german guns a higher HE kill than the Hispano.
Also from
http://www.quarry.nildram.co.uk/CannonMGs.htm
"The German cannon were not exclusively loaded with Minengeschoss, but used them mixed with older-type HEI-T shells (retained because, unlike the M-Geschoss, they could carry a tracer) and later some API rounds as well, in varying proportions." No doubt plenty AP if on a ground attack mission.
Also see this site which gives detailed descriptions of the various recommended mixes used by the germans in there ammunition belts ie mixed HE and AP
http://www.geocities.com/capecanaver...n/fgun-am.html
So Marek_Tucan would seem to be correct here.
Best Regards Chuck.