99.9% sure that .54 was the biggest caliber in a production muzzleloading rifle, but they also made 12 ga smooth bores, so technically that would be about a .72 cal smooth bore.
Hard telling what Tony made as far as custom rifles, but as far as production muzzleloaders I have only seen .36 cal, .45 cal, .50 cal, .52 cal, .54 cal, and 12 ga.
They made several center fire calibers for the KP1, and I think a couple rim fire calibers also.
