Articap - I was thinking the same thing. The AR would be the easiest gun to build as a muzzleloader. You get a barrel and have a breechplug installed that is drilled and tapped for a nipple. You modify the bolt and firing pin for percussion caps and finally, you have to make a special capper & decapper as that tiny firing port would be hard to reach inside. Of course, with the AR you can always pull out the take-down pin and swing the lower receiver down to get access to the percussion cap. The AR's (California evil) 20-round magazine is converted into a cap box or a possibles box for your jag, stuck ball remover, spare nipples and nipple wrench.