Arizona,

Precthl made both the action and the complete rifle Alf pictured when Mauser turned 100 years in 1998. He made 100 in 416 Rigby, and 100 in 375H&H. I have one in 375H&H.

His website is: Pretchtl (Golmatic)

Another German option is Karl-Heinz Ritterbusch who makes both actions and complete rifles.

Sigarms now owns the Mauser name, and makes Mausers using Prechtls actions as far as I know: Sigarms Mausers.

Erik