Impossible to say that when looking at a closed action. Most of the metal work is in lengthening the magazine box and correspondingly the magazine well of the action itself. Usually quite a bit is taken from the feed ramp/lower lug recess area and side rails. There is no need to mill a notch into the rear of the receiver ring which of course is 'eating' into the back of the top locking lug recess. Mauser themselves milled such a notch into their Type B for the 30.06 but this was more to accommodate charging the magazine from a clip but when loading 404 rounds into an opened up standard 98 Mauser they drop down in the lengthened magazine easily.

Winchester did similar metal work when opening up their standard pre'64 Model 70's to a 'magnum' action for the 375H&H etc.

Aside from all this it is a pleasure to see such fine workmanship on such a fine rifle and of course for one of the finest cartridges for African large and dangerous game.