You can use a 22 lever, pump or single shot. Basically anything with an exposed hammer. The smallbore match also has separate categories for pistol caliber rifles - main match rifles. I'm sure we can come up with extra rifles, or just share one during the match.
Also remember that we alternate months with one being small bore and pistol caliber, and the other month being Cowboy Silhouette - rifle caliber (lever or single shot) guns on full size silhouettes at 50-100-150 and 200 yards.