Cowboy action handguns follow traditional lines. The .45 Long Colt is the most common. The .38 Special is up there too, because of its light recoil. There are some shooters that shoot original Colts, but they're getting hard to find. There are lots of Colt replicas, but the Ruger Vaquero is probably the most common handgun because of its price and durability.
Most shooters employ traditional two-handed grips.
A special Duelist category that demands shooting revolvers one-handed and unsupported. There's also a black powder category. Rifles must be chambered for a pistol caliber, May said. A lot of guys shoot .44 Specials. The Marlin Cowboy is very popular and the Winchester 92 is very common.