Ho-5 used the weakest 20mm ammo of WW2, the 20x94.
But there are lots of problems with other guns ingame, like too powerful Shvak (second weakest 20mm ammo of WW2, barely better than 20x94), too weak Shkas, too weak UB (far superior to .50 Browning in RL)
check this:
http://www.quarry.nildram.co.uk/WW2guneffect.htm