Welcome to the forum. Rules are to join in, have fun, and play nicely with the rest of us kids.
I don't know the answer to your question. I've seen the TCR-83 Aristocrat action for sale on line before, but don't recall ever handling one. Also, just because someone out there has done something by way of custom chambering doesn't mean the design was intended to handle it. For that reason I would just call Thompson Center customer service and ask if that 45-70 chambering was ever done by Thompson or if they know a reason it shouldn't be done? (603) 330-5659.
A forum community dedicated to Sport shooters, owners and enthusiasts. Come join the discussion about optics, hand casting bullets, hunting, gunsmithing, styles, reviews, accessories, classifieds, and more!