And he blow out puffs of smoke from his pipe for things like poison spray, arms of hadar, and gaseous form. It'll use a pistol for single target, shotgun for cone/aoe, and the rifle for long range/"in a line" damage.
During different types of spell, they'll spin the weapon on their finger and it transforms into either a pistol, a double barrel shotgun, or a hunting rifle (all are purely cosmetic for flavor). I like the idea of them creating a bullet for the spell when they cast and firing off the weapon for each die of damage the spell does. I went with blade pact to allow my character to use their weapon as an arcane focus. So far, the main build idea I've come up with is 2 artificer (gunsmith, bag of holding or goggles of night), 7 fighter (eldritch knight, close quarters shooter), 11 hexlock (blade pact). But, I really enjoy the idea of a cowboy wizard who refers to magic as "hokus pokus". Ok, so this character isn't quite fleshed out that much.