VGAS, Vertical Gun for Advanced Ships.

[TomS]

So basically a modern mortarized gun, only dropping the gun mechanism to load rather than dropping charges down a barrel. Probably even acts as a recoilless system to save shock against a superstructure. Kind of looks like the charges and projectiles were separately loaded rather than assembled. I wonder if they used piping to simplify the charge chamber loading where both barrels shared common charging chambers. That would allow simultaneous fires but with an allowance for more time to cool each chamber, since charging chambers could outnumber barrels. Imagine an odd number of charging chambers feeding an even pair of barrels.

If you look at the drawing we have of VGAS, the two guns and magazines are actually separated by a bulkhead. That means the guns are likely fully independent. Each one looks to use a loading drum for the immediate ready use rounds, probably enabling a relatively quick burst of 5-6 rounds MRSI. Additional rounds would be mated up as the projectiles and charges feed into the drum.