Talk:Type 91 Armor Piercing Shell/@comment-24116043-20140501011518/@comment-24473957-20140502213509

According to the Japanese wiki

2 main guns (red) + 1 AP rounds + recon plane can trigger:

cut-in attacks that does 1x150% damage

double attack that does 2x120% damage

noraml attack that does 100% (normal) damage.

So technically AP rounds can do all of the above depending on your RNG.

Like handgun said, for the current event though its better to leave them at storage. Bosses like E3 and E5 are considered ground installations and not ships, where Sanshiki rounds are more effective. (ie. armor piercing rounds on soft target is going to pass clean thru without doing as much damage as shrapnel)