The XM813 30mm Autocannon

[Mobhack]

Class 4 AAA used to button up (to 0 shots) when pinned. Since about 10 years or so back, it loses some shots if pinned, but not to 0 as of old.

One reason a cupola type MG is good for RWS style mounts rather than a class 4, the cupola MG if the vehicle is buttoned does not lose shots. But cannot fire at planes, one trade-off amongst many.