Not enough space in a fighting aircraft for any kind of rifle. No firearms attached to or tucked in the rocket powered lounge chair they drive around in either. It gets separated from the driver(who will likely be hurt from using it)when used anyway. Transports and helicopters, maybe.
"...cannot follow a B-52..." That's what the Boat People are for. Assuming they're close enough. Only 76 B-52's left anyway. Only 66 B1B's.
You won't be dismounting a Bofors cannon or a mini-gun. Nobody's going to ride the aircraft down either. That quick, sudden, stop at the end of the fall, hurts.