Too late. A Giff racial feature is that they ignore Reload. They are after all, spiritually connected to firearms via their gods.
Reading up on all of the guns in 5.x. Funny enough, for all the connection between Giff and firearms, nothing is described in the Spelljammer books that I can find except for the Musket and Double Barreled Musket attack descriptions in the Giff monster stats.* The 5.24 DMG has guns but they are obviously modern weapons with Burst Fire abilities and no prices as they are meant to be found in special markets in such places as the City of Brass (IIRC). No prices anywhere. Is there any other references I'm missing?
For my own treatment, I'm dividing up rules by how I want them to affect my game, as adventurer's weapons, good for equipping infantry, or just not quite as good as bows. Balancing the damage, cost, range, and other factors to suit that usage for whatever I want for a particular campaign.**
*Really sort of brings home what a shoddy job that set of books was. It's why I bought the 2E Planescape book rather than the 5E one when I became interested. Looks like it was all done by Chris Perkins. Another thing I can blame him for.
**Currently ignoring them as siege weapons, which is where they really should come in with importance for some mediaeval or early modern weaponry.