Well, this is the short version:
Rifles: Lever or slide action, tubular fed, exposed hammer, pistol caliber rifles or carbines manufactured between 1860 and 1899, or a modern "clone" of such a rifle.
Pistols: This is devided by catagory. Basically, any single action revolver manufactured before 1896 or a clone of that design. Sights, percussion or cartridge, and smokeless or black powder help determine the shooting class.
Shotguns:Any side by side or single shot typical of the 1860 to 1899 time frame, WITHOUT automatic ejectors, with or without exposed hammers. Lever action shotguns with exposed hammers and pumps such as the 1897 Winchester with exposed hammers are allowed. 20 guage to 10 guage, number four birdshot or smaller.
This is a rough outline. For details, visit
www.sassnet.com ,this is the SASS home page. Click on the "Shooter's Handbook" on the left side for a complete listing.