Never heard of a "lead only" rule in colorado ML book. I just checked and the powerbelt is legal. They just dont allow sabots because a sabot is an under sized caliber. In order to hunt elk with a muzzleloader in colorado, it must be a .50 or bigger firing a bullet 170 grains or more in a .50 and 210 grains or more in .54 or larger. Any bullet is Legal. Just No sabots. A power belt is not a sabot. Get a box and try them out. I know the old powerbelts work great,havnt tried the new ones yet. But get a box of grainage that you want and go practice. You will need to get more yardage out of that rifle than 50 yards. For the price you paid for that gun, I would really get my butt in gear and buy some powerbelts to try out. Good luck to you on sighting in the rifle and on the hunt.