The closest thing to an autocannon that BA can haul around is the Bearhunter AC system. Don't forget that most AC-2s (i.e. one of the most common) are 75/76mm cannon based on the ARES cannon concept (which had two versions, a 75mm cannon and a 90mm cannon, both of them able to fire three rounds in a second), probably with some ETC (Electrothermal Chemical) technology put in to give the general 'hypersonic/hypervelocity' descriptors for the rounds going downrange.
On a quick note of that tangent:
It's surprisingly hard to track down specs for said ARES cannon, given that it only existed in an obscure prototype program and half the stuff on the Internet about it is from Sparky's clown brigade. Some sources do refer to it as "hypervelocity", but the only actual muzzle velocity figures I'm seeing are 4800 feet per second for the actual gun, plus penetration testing of the "Delta 3" prototype 75mm DU rounds at 4800 FPS and 5400 FPS with performance on par with the then-standard 105mm M774 round, and later testing of the further improved "Delta 6" prototype at unspecified velocity with 430mm RHA penetration at 2000 meters range. Said Delta 6 was basically squeezing every ounce of performance they could out of the round, and that is damn impressive penetration for something so small, but it wasn't enough to handle expected future threats so the program was cancelled at that point.
All of that would place them at high velocity, but not full-fledged hypervelocity.
Edit: That said, what is your source for AC-2s being 75-76mm? Per Sarna, the Armstrong AC-2s on the Vulcan battlemech are 60mm, and the Whirlwind-L AC-2s on "older" Blackjacks are 40mm; those are the only ones mentioned with explicit canon calibers.
Last edited: