I got the Armamentarium from Xur, and I've gotten the abilities on it, they don't seem to work the same way for machine guns than rockets. Noted Effects: Invective: Allows for 5 extra bullets to be carried Ice Breaker: No effect (normal), all bullets kept in clip (6), and doesn't allow reload, so the ability naturally doesn't add more. Rockets (Primed Khan RS/4 with a clip of 2): Allows to carry an extra rocket, and allows you to get 3 rockets instead of 2 from a heavy ammo box. Machine Gun: It only seems to add 1 extra bullet to the ammo pool for some reason. I have the Zombie Apocalypse WF47 with the bonus ammo clip, which allows me to carry 225 bullets total. When I have this chest equipped, the total amount I can carry is 226. I'm wondering if this is a bug, or if 226 is the universal maximum amount of heavy ammo that can be carried.