Well... using the 30mm autocannon with a riot shield is going to be difficult, since we've established that model being pretty much the Dragunov SVD in proportion to a FRAME... so you can probably imagine how ungainly it'll be to shoot it one-handed.

The AFC-40/L Halabrad-Phell 25mm autocannon is going to be easier to wield, but something smaller like a 23mm or 20mm is probably going to be more like the size of a one-handed operation.