then consider getting it reamed to .30 mauser.
That would ruin the gun. .30 Mauser is much too long for the Luger magazine and action stroke.
.30 Luger was not an "oddball" chambering. As said above, it was the original caliber for the gun and was quite popular with the Swiss, Finns, and Portugese armies adopting it. There were a lot of commercial sales, only some of which were due to Treaty of Versailles restrictions on German gun production or Italian law. Heck, the US Army bought 1000 of them.