How to increase base ap without increasing the hm lvl?

[Provois]

Hello

 

I'm a BM and met a other Bm with the same hm lvl (hm 9) with almost the same gear then me (same SS, same accessories, same weapon and same Hm energy) he only has a gem what give him 5 ap what i don't have. So he should only have 5 ap more then me but nope he has 12 more then me because he has 119 base ap and i have 112 base ap. I know that the base ap is increasing with the (hm) lvl and is a bit different between the classes but like i said this guy has the same class and (hm) lvl then me.  So what did this guy to get 7 base ap more?

[LunaticAzure]

There's 2 achievements that give ap. One gives 3 , the other 7. To get the 7ap you need to beat 4 man Avalanche Den 100 times. Also, you can only have one achievement stat bonus on at a time. Say for example, you can't have both accuracy and ap on, you can only have one or the other.

[Provois]

Thx, i completely forgot about the achievements.