"Trashcan' that it is, I could see chucking up in a collet in the lathe and just turning in a lube groove or two. Yeah, it is a little futzy, but we do a lot of futzy things in this hobby.
BTW, a friend used to cast a 180ish gr. RN, probably something for a 35 Rem., and in our local 'smallbore' BPCR shoots the guys with .38Spl and .357M chambered rifles did right well on the steel and scored well on paper. IIRC, that bullet loaded into .38Spl cases fit nicely in a .357M chamber.
Ed Harris, when at Ruger, developed a rethroating reamer for the 'problematic' .357M No.1s (they didnt group well with standard tooling) and it was magic. He has written a fair bit about it and I know Ive seen it in The Fouling Shot, the official publication of The Cast Bullet Assoc. I suspect that the improved throating of the Forum .357Maxi reamer is largely responsible for the generally improved accurracy.