As far as I know (but how far is that?) you have the choice between linseed oil, linseed oil
- and, for special cases - linseed oil.
In other words, IMOH, there's no question.
If you have been confused by seeing military Mausers finished with Tru Oil, tung oil, urushi, shellac, floor varnish, treacle, or whatever else, this is because they have all been "improved" by later owners, not by the Mauser factory.