+1 thunderbolt dart rifle mk.1.
Probably best to do the dart rifle, it lacks range, but, well, is awesome. We really do need range though. And yes, some sort of revolver cannon. It would require a fairly light round, as far as cannons go, but we could probably manage 6 pounds, just not any more than that, although maybe four would be more sensible. I imagine that it would have relatively low power, due to not being cast as a single piece, and the rate of fire would probably be only slightly improved, and even that would require using all of the chambers(probably three) which would be a downside because... In an emergency you could fire in very(for a cannon) quick succession. It would mostly be a defensive piece, used to deliver unparalleled canister barrages against assaults, but if it could be moved while loaded it would be able to provide a burst of fire to secure its posting after being repositioned. If it worked well it might even be possible to upscale it to a prestige piece, the same drawbacks would apply, making it a pain to upscale, but the ability to temporarily increase the effective count of guns could make accoutrements(such as longer barrels, rifled barrels, custom reloading platforms, crew armour, aiming winches...) more practical.
But for now, cavalry with R.P.G.s should hold us together for the short-term.
P.S.
I think that the G.M. took pity on the automatic pistol and made it awesome, it should be simple enough to revise it to be at least vaguely safe.
P.P.S.
the other fort stole my shield idea, I must be avenged!
P.P.P.S.
did anyone else get a "landing ship" vibe from the loyalists? It is a good thing that we didn't fight a long and bitter war to gain extensive swathes of coastline with them...
P.P.P.S.P.S.
Actually, the dart rifle would probably be very useful against a landing, moreso than comparatively slow artillery pieces.