Hello @Sea Turtle. The Missouri guerrillas who operated in the western and central parts of the state (and perhaps other bands, too) favored revolvers, although some certainly carried shotguns. I imagine there were carbines and even revolving rifles later, as these guys picked up a lot of equipment and uniforms (for disguise) from the soldiers they killed. But the preference was revolvers, and the typical guerrilla carried as many as possible. Some were holstered, one or two more were tucked into the belt, and some were carried in saddle holsters. The idea, of course, is that these could be pre-loaded in camp, and they would provide overwhelming fire power against soldiers armed with single shot rifles.
But in nearly every photo you see of a Missouri guerrilla, you'll notice they are wearing brightly embroidered over-shirts with large pockets. These could be used to carry extra caps, balls, and pre-made paper cartridges. The shirts served as their uniform, too. I assure you that every soldier and citizen in Missouri recognized a guerrilla shirt at first glance. In the movie "Ride With The Devil" there's a good short scene where Quantrill's raiding force stands mounted on a hill, waiting for the order to charge into Lawrence. Someone yells "Take off your coats, boys. Let 'em see who we are!" That's a direct reference to showing off their guerrilla shirts.
I mentioned that the guerrillas often disguised themselves as federal or state militia. They did this so they could pass through hostile territory, or to get close to a target for an ambush. For example, during the 1864 raid on Fayette, Missouri, most of the force was outfitted in militia uniforms, and this allowed them to get into town without resistance from the garrison there. During times like this, they'd have carried captured belts, cartridge boxes, etc. etc. During the infamous massacre of furloughed soldiers on the railroad platform in Centralia, Anderson's men ordered their victims to strip to their long johns before they were shot. Undoubtedly, this is so they could acquire a quantity of uniforms without bullet holes or blood stains.
In this famous photo of teenaged Jesse James, you can clearly see two revolvers tucked in his belt and one in his hand. You also see his guerrilla shirt, with a heavily loaded breast pocket sagging under the weight it carries. His pinned up hat brim and feather plume in back are all part of his uniform.