It is my understanding the wording on the "cannot be loaded from the breech during the muzzleloading seasons" came from the various Sharps type rifles which could technically be loaded from either the breech or the muzzle. This part of the reg has been in there for longer than the T/C Encore has been around.

The only muzzleloaders that aren't legal in Colorado are the double barrel rifles. What you load in it, however, has to be fairly primitive - no sabots or pellets. Must be full caliber conicals (or round balls) using loose black powder or black powder substitutes. No scopes or red dots.

According to several of the big sporting goods stores, the most popular bullet is the Powerbelt and the most popular powder is loose Triple 7. Most folks are currently using in-line rifles with fiber optic sights.