Legal firearms in per Wyoming G &F are:
Big and Trophy Game
Legal firearms for BIG or TROPHY GAME must have a barrel bore diameter of at least 23/100 of an inch and be chambered to fire a centerfire cartridge not less than two inches overall length including a soft or expanding point bullet seated to a normal depth; or a muzzleloading rifle which has a barrel bore diameter of at least 40/100of an inch and a charge of at least 50 grains of black powder or equivalent (Pyrodex), or a muzzle-loading specialty single shot handgun which has a barrel length of not less than ten (10) inches, a bore diameter of at least 45/100of an inch and which propels a projectile of two hundred forty (240) grains at not less than five hundred (500) foot pounds at one hundred (100) yards.
In addition, a hunter may use any other cartridge fired from a firearm that has a barrel bore diameter of at least thirty-five hundredths (.35) of an inch and the cartridge generally delivers at least five hundred (500) ft-pounds of impact at one hundred (100) yards and cartridges used are loaded with a lead, soft, or expanding point bullet.