He was using a heavy Douglas barrel on one of the good Mauser actions with a custom stock.

The cartridge case is the longest that will comfortably fit in a standard Mauser action, or any rifle action designed to chamber the 30/06.

Derived from the FN Model 30, based on the Mauser action dating to the G98, with three-piece bolt and a five-round magazine.

Using a Mauser 98-type action, the 54 was a less-expensive derivation of the limited-production handmade Model 51 "Imperial" of 1919.

The length of the case is the longest that would fit in a standard Mauser action.

The Mauser action is a copy of the Gewehr 98 model rifle's action.

The FR-8 was developed from the Model 1943 short rifle, which was based on "large ring" Model 1898 Mauser action.

The rifle was a single shot bolt action rifle using the Mauser action, with rounds manually loaded into the chamber.

While many .375 H&H rifles were built on the longer magnum Mauser actions, these actions were considerably more expensive and rarer than the standard actions.

Other rifles, not rarely based on the Mauser action, were chambered for this cartridge too.