Agree with the above. Get a set of the Lee dies - very economical. As you will only be using them to neck-size the fired cases, it is unnecessary to buy anything more expensive. Simply set up the resizer as usual, then back it off about 1/4 to 1/3 of a turn so that only the neck is resized. the remaining unsized ring at the bottom of the neck serves to center the once-fired cases in the chamber. If you can get hold of a mould that casts bullets around .446"-.447" diameter, you may be able to get away with no resizing at all! If you want maximum accuracy you will anyway be loading individual cartridges and not using the magazine, and the sheer inertia of the heavy lead bullet means that a crimp is not needed for proper combustion. Use din this way, the cases should last indefinitely PROVIDED that you wash them out soon after shooting (same day!). Leave fired cases for a couple of days and they will start to show a green patina on the inside - which is, of course, corrosion.
BTW, reload with BP only. The rate of onset for smokeless powders is far too fast, and the M1871 or 71/84 rifles had just one locking lug at the side. So the faster the onset as the powder ignites (i.e. the increase in pressure and thus the "acceleration of the acceleration") the more the system tends to bend laterally from what is effectively a shock loading . This problem was well-observed at the time, but only finally solved with the 9.5x60R M1887 rifles for Turkey, which had an extra bolt lug added on the other side, to even up the lateral forces.
And the large BP cases make it fatally easy to load an excessive charge of smokeless or even a double load. Stick to real BP in grading 1-1/2Fg or 2Fg and the Mauser will perform about as well as you can point it.