Thanx for that, Kurt (split and all). Im sure the question of what the Huntsman barrels fit still is good to go for this forum. By the way its stated I assume the .58cal. are only on Huntsman barrels.
With my 'Snider' HB conicals muzzleloaded I think it would work out since the Snider conversions were on the British .577 (nom. 58ca.,) muskets with a slow twist too. Later versions made, not conversions, ended up with faster twists.
But.......my 'always a project around the next corner' mind jumped right into, 'what if' mode.
Any .58 is quite a thumper and my little Snider Cavalry Carbine is a beast (a cute little beast); a Handi version would be dandy.