FYI from the 2023 CO Big Game Brochure, HUNTING LAWS:
MUZZLELOADING RIFLES & SMOOTHBORE MUSKETS
a. Only legal muzzleloaders allowed in muzzleloading seasons.
b. In-line muzzleloaders are legal.
c. Must be a single barrel that fires a single round ball or conical projectile.
d. To hunt deer, pronghorn or bear, conical bullets must be a minimum of .40 caliber, and round-ball bullets must be a minimum of .50 caliber.
e. To hunt elk or moose, conical bullets must be a minimum of .50 caliber, and round-ball bullets must be a minimum of .54 caliber.
f. From .40 caliber to .50 caliber, bullets must weigh a minimum of 170 grains.
g. If greater than .50 caliber, bullets must weigh a minimum of 210 grains.
h. Shotshell primers and B.O.R. Lock MZ System bullets are legal.
i. Pelletized powder systems are prohibited during muzzleloading seasons.
j. Cannot be loaded from the breech during muzzleloading seasons.
k. Only open or iron sights allowed in muzzleloading seasons. Fiber optics and fluorescent paint incorporated into or on open or iron sights are legal. Scopes or any sighting device using artificial light, batteries and electronic gear are prohibited during muzzleloading seasons.
l. Sabots are prohibited during muzzleloading seasons. Cloth patches are not sabots.
m. Smokeless powder is prohibited in muzzleloading seasons. Black powder and black-powder substitutes are legal.
n. Electronic or battery-powered devices cannot be incorporated into or attached to muzzleloader during muzzleloading seasons