So, I'm not 100 percent sure this is a bug, but I figured I'd post.
Two issues here:
1) Most APU spells are not labled by dmg type, frost beams for instance don't list what type of dmg they do (and in what ratio) like most weapon ammos do.
2) (Not sure if this is an actual bug), The APU energy barrel seems not to do energy dmg.... it's listed as pierce and xray.