Hi Andy
I had a look at some other aircraft weapons and here is what I turned up, hope it is of interest to you.
These links mention that 20mm MG-FF 167 and 20mm MG-151 166 Have AP Ammo.
http://www.warbirdsresourcegroup.org/LRG/mgffm.html
http://www.warbirdsresourcegroup.org/LRG/mg151.html
These weapons get a penetration value of 2 shouldn't this be 4 like say the hispano 20mm?
carried by,
 Fw 190A-8 121
 Fw 190F-8 237
 Fw 190F-3 242
 Me 210a 901
 Me 410B-1903
 Bf 109G-2/R1 122
 Bf 110D-2 123 
 Hs 129 B-1 128
 Hs 129 B-3/Wa
 Hs 129B-2 240
 Fw 190 D-12 243
 Fw 190F-1 236
 Fw 190 D-12 243
 Ju 87D-8 Stuka 487
 Bf 110C 894
 Bf 109E 906
 Bf 109E-7 907
 Bf 109F 908
 Bf 109F-2 909
 Fw 190A-4/U-3 913
 Fw 190R-6 914
 Fw 190F-8/R-1 915
 Fw 190F-9/Pb1 916
 Fw 190F-9/Pb2 917
 Bf 110C-4/B 895
 Bf 110C-7 896
 Bf 110E-2 897
 Bf 110NF 898
 Hs 129 B-2/R-4 900
Quotes from
http://www.quarry.nildram.co.uk/tankbusters.htm
30mm MK-101/103
"Various AP rounds were used, but the most effective was the Hartkernmunition, which had a penetrating core of tungsten carbide sheathed in a light-alloy shell with a sharply-pointed profile. This could penetrate 75-90 mm / 300 m / 90 degrees (depending on the type of armour)"
Previous Version 6 of the game had the penetration of 9 now 4 in Winspww2.
Carried by
Hs 129 B-1 128
For interest you may want to substitute some of the 30mm MK-108 168 carried by these for 30mm MK-101 169
Fw 190F-8 237
Bf 109G-2/R1 122
Fw 190 D-12 243
Bf 110NF 898
3.7cm BKannon 207
"It also remained clip-fed, with a maximum capacity of just 12 rounds. It mainly fired Hartkernmunition ammo, capable of penetrating up to 140 mm / 100 m / 90 degrees"
Previous version 6 of the game had penetration 14 now 5 in WinSPWW2, shouldnt it be 14?
Carried by
Ju 87G-1 Stuka 120 
Ju 88P-2 234
5cm Bord Kannon 208
Previous version 6 of the game had penetration 16 now 7 in WinSPWW2, Should be at least 9 as same ammo as pak 50. If firing tungsten shot should be 15.
Carried by
Me 410A-1/U-4 902
Ju 88P-4 235
7.5cm BKannon 209
"The fully-automatic BK 7,5 with a 12-round rotary magazine. This could penetrate 132 mm / 500 m / 90 degrees"
Previous version 6 of the game had penetration 18 now 12 in WinSPWW2,should have penetration of 13 not current 12 as same ammo fired as the PAK 40. If firing tungsten shot should be 17.
Carried by
Ju 88P-1 233,4,5 209
Hs 129 B-2/R-4 
Hs 129 B-3/Wa 129
? Hs 129 B-2/R-4 900
Although the game uses 30mm MK-101 maybe this should be substituted with 30mm MK-103 which had better ROF.
See 
http://www.quarry.nildram.co.uk/WW2guneffect.htm
http://www.warbirdsresourcegroup.org/LRG/mk103.html
Best regards Chuck