Board Thread:Off Topic/@comment-27447621-20180223225208/@comment-27144409-20180910190129

Well first I had to make sure you weren't suggesting imitating the broadsider (basically an old blackpowder muzzle-loading cannon in a recoil reducing harness) from Fallout 4.

I actively discourage and avoid the use of obsolete black powder muzzle-loaders. Port and Scarlet are on my deathglare list.

To my knowledge, most battleships (which had armament comparable to battlecruisers) used high-exploisive shells, so aside from relatively slow velocities.

For unique flavor I'd recommend a recoiless rifle, which offers relatively high-caliber shells, while remaining man-portable. (beware the backblast)

Alternatively you go "full" Coco and use an Oerlikon/Re 20mm (maybe 30mm)( cannon configured for semi-auto fire, and loaded with high ex rounds, which is what I think you really want. Keep in mind that that is APC/IFV/light tank levels of firepower you're hauling around now.