I know of nothing in the Wyoming statutes that has a requirement for Bison, but the other game animals have the following by statute:
Section 4. Firearms, muzzle-loaders and cartridges that are legal for the taking of big or trophy game animals.
(a) For the taking of bighorn sheep, elk, moose, mountain goat, black bear or grizzly bear by the use
of a firearm, a hunter shall use:
(i) Any center-fire firearm of at least .24 caliber and firing a cartridge of at least two (2)
inches in overall length, or any other cartridge of at least .35 caliber and at least one and one-half inches (1.5)
in overall length, and using an expanding point bullet; or,
(ii) Any muzzle-loading rifle or any muzzle-loading handgun of at least .40 caliber and
firing an expanding point bullet using a charge of at least fifty (50) grains of black powder or its equivalent; or,
(iii) Any shotgun firing “00” or larger buckshot, or a slug.
(b) For the taking of antelope, deer, mountain lion, or gray wolf where designated as a trophy game
animal, a hunter shall use:
(i) Any center-fire firearm of at least .22 caliber (excluding .22 Hornet) and having a bullet
weight of at least sixty (60) grains and firing a cartridge of at least two (2) inches in overall length, or any other
cartridge of at least .35 caliber and at least one and one-half (1.5) inches in overall length, and using an
expanding point bullet; or,
(ii) Any muzzle-loading rifle or any muzzle-loading handgun of at least .40 caliber and
firing an expanding point bullet using a charge of at least fifty (50) grains of black powder or its equivalent; or,
(iii) Any shotgun firing “00” or larger buckshot, or a slug.