I was given a 1871 single shot Mauser a couple of months ago that is in shoot-able condition. One of my shooting friends who also has one showed me how to re-form 300 win mag brass into quite acceptable cartridges. I have put about 50 rounds thru the gun and every one fired and ejected perfectly. I like this old gun and will probably look for a 71/84 repeater.
https://www.youtube.com/watch?v=m0E_Hly-uE0
Also have some 458 win mag brass coming which will save the fire forming.