Talk:Type 1 Armor Piercing Shell/@comment-5496371-20150529013649/@comment-26872187-20150909023801

From what I've read, AP shells (and small/medium guns too) get additionally 3 FP and 6 ACC from +9 and 2 FP and 4 ACC from +4.

So, comparing a Type 91 +9, a Type 1 +0 and a Type 1 +4, we get:

Type 91 +9: 11 FP (8+3), 7 ACC (1+6)

Type 1 +4:  11 FP (9+2), 6 ACC (2+4)

Type 1+0:    9 FP, 2 ACC

So, unless you upgrade your Type 1 to more than +6 (which will require additional Type 1 shells and thus be very expensive), an upgraded version of the Type 91 should always be better than the Type 1. So, don't upgrade the Type 91 to Type 1, I'd say, unless you really have an abundance of Type 91 +9 shells :-P