The 71/76 came out prior to the 71/84 of course. Did I say or imply otherwise - if so, sorry.

The original 71 and the 71/76 that I have both had .457" groove diameters - even though the bullet that was shot, was .446". The chamber will not allow a larger bullet to be chambered than the .446" diameter.

An undersized paper patched soft bullet, driven by black powder will expand to fill the grooves. Being unable to load a grooved, lubricated bullet is why I rechambed mine to a larger necked ctg. I wanted the .450 Alaksan Reamer for another job regardless and decided to re-chamber my Mauser rifle as well.

A simply neck throater would also have worked, thus leaving the original body of the chamber alone. That would have allowed me to use .43 Mauser brass but with the proper sized bullets. At the time I got my rifle, .43 Mauser brass was not available to me easily or cheaply enough, while .348 Winchester brass was. Now, even Starline makes that brass.

The later 71/84 had a .446" groove diameter, proper for the bullets cabable of being chambered in the case.