Firearms and Ammunition Regulations
No person shall take into or possess in the game fields or forests of Wyoming any fully automatic weapon or device designed to silence or muffle the report of any firearm. Firearms and cartridges which are legal for taking Big or Trophy Game, or Wild Bison, are described in the following paragraphs.
Wyoming statutes authorize the use of a firearm which has a barrel bore diameter of at least twenty-three-hundredths (23/100) of an inch and is chambered to fire a center-fire cartridge not less than two (2) inches in overall length, including a soft or expanding point bullet seated to a normal depth or a muzzle-loading rifle which has a barrel bore diameter of at least 40/100 of an inch and a charge of at least fifty (50) grains of black powder or equivalent, or a muzzle-loading specialty single shot handgun which hasa barrel length of not less than ten (10) inches, a bore diameter of at least 45/100 of 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, the Commission authorizes 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) pounds of impact at one hundred (100) yards and cartridges used are loaded with a lead, soft or expanding bullet point.
Wild Bison shall only be taken with a firearm which has a barrel bore diameter of at least twenty-seven hundredths (27/100) of an inch and is chambered to fire a center-fire cartridge not less than two (2) inches in overall length, including a soft or expanding point bullet seated to a normal depth. The cartridge shall have a minimum of a one hundred fifty (150) grain bullet. Wild Bison may also be taken by the use of muzzle-loading rifles having a barrel bore diameter of at least 50/100 of an inch and a charge of at least one hundred (100) grains of black powder or equivalent, only on lands off the National Elk Refuge.
Personal Note: I highly recommend using Remington® Core-lokt or Nosler® Partition bullets. I have not been impressed with the ballistic tips or some of the newer bullets.