The chambering is 11.15x46R. This is NOT the same as .43 Spanish.
But the proper die set from Lee has the same price. Which is an absolute bargain for such an antique caliber.

There is no difference in the chambering between an M71 and an M71/84.
As can be seen "Mauser Bolt Rifles" by Olson, the original cartridge for the M71 had a 386 gn paper-patched round-nose bullet. This was changed to a flat-nose for the M71/84, because the rounds were loaded nose-to-tail in the tubular magazine.

At 100 yards you will not notice any difference between the two, but at 300 and above the round-nose will have a slight ballistic edge.

The original cartridges had a 77 gn charge. For target shoooting I recommend a heavier bullet, approx. 450-470 gn. The longer bullet plus the grease cookie you will find you need under the bullet to be able to shoot long strings without cleaning reduces the powder capacity to 67-70 gn of Swissicon No. 4 (1 1/2FG).

In good condition, these rifles can respectably compete with the 45-70 Trapdoors. The price range mentioned by Hugh Uno would be the same here in Mauserland, but in euros. Grab it.

Patrick