Bill,

I do not believe that an original Model 71 barrel has enough meat to it to be rebored & rifled to 50-110.  Replacing the barrel to a heavier contour would require swapping out the forend stock.  That all stated, I suspect that a Model 71 could be reworked to the 50-110 EX if someone was motivated and talented enough to do it.  The real question is “Why” ?  Ballistically the 348 WCF is a much superior cartridge.

Bert