Personally I'd think weapon ones should be more connected with shots it fire, eg. shotgun would have 2 or 3 shells as icon, nex would have a trail, RL - a single large rocket. I named a few weapons that trip me up in such context. Proposed chaingun one seems fine.
Ammo icon would be most obvious weapon icon using specific kind of ammo contained in some geometric shape
Ammo icon would be most obvious weapon icon using specific kind of ammo contained in some geometric shape

