If you haven't checked out if it would or would not chamber a round with a .446 bullet I would take the time to check it out with either loading a round or making a chamber cast.
I have a Early Farmer that John rebarreled with a 17 twist and I think he used Steve Rhodes reamer doing this and is so I would use this bullet.
https://www.buffaloarms.com/443-495...1-cavity-arnie-seitz-design-jim443495eppOr this one,
https://www.buffaloarms.com/434-470-grain-paper-patch-bullet-mould-1-cavity-flat-base-jim434470I hope you were able to get some brass with it.
Kurt