It may very well hold up at least for a while until the underlug sets back and the barrel gets loose, even the 500 S&W Handi has done that too often, although H&R will replace the barrels on those, that wouldn't be an option after the rechamber. But even hot 45-70 loads have too much recoil for most folks, a Limbsaver pad and weight or MRS in the stock would help in that respect.
Tim