The X-Caliber Adaptor Set is designed for use in any condition and with any ammunition available. It was originally designed with two calibers, a rifled .22 LR and a smooth bore .12 GA. The 12 GA Rifle can fire up to 12 different calibers thanks to the 8 steel adapters supplied. In addition to the two original gauges, adapters allow you to shoot 8 pistol calibers (.380, 9mm, .357Mag/.38SP, .40S&W, .44 Mag, .45 ACP, .410/.45colt) and two shotgun calibers (410 ga, 20ga). It combines the flexibility of a shotgun and the power of a rifled gun.