Here's mine, a 71/76 - earlier version with a .457/.458" groove diameter, not .446" as in the M71/84 model. The deeper grooves were thought to help with longer shooting strings, in holding powder fouling from the .43 Mauser's 77gr. charge yet getting a good grip on the paper patched 370gr. soft bullet that would expand into the grooves, filling whatever room was available.
Unfortunately for shooters today having this model, who don't want to put up with mediocre accuracy of the over expanded (up to .011") paper patched bullet, the chamber will accept no larger a bullet than a .446" bullet. The bore diameter is nominally .437/.438". In the model 71/76, such as my carbine, the depth of rifling runs .010" to .0105" per side.
The alternatives for someone wanting to shoot this model are to either put up with the accuracy of the groosly undersized bullet, or to open up the chamber's neck to allow a larger bullet, ie; one of groove diameter.
Since at the time I acquired my rifle, .43 Mauser brass was not available to me, I simply re-chambered my rifle to the .450 Alaskan, with the pilot turned down to .437".
The results with a .45/70-type load of smokeless and with black powder are equally satisfying, even though the bore is in poor shape. Fire lapping helped immensely.
At 6 pounds, it boots quite smartly.