The Cutts Compensator for rifles was advertised as a "30 caliber" device. I assume it can be used for a .375, but don't know for sure. I assume it was installed over the muzzle after drilling it to the proper size, then soldered. The Cutts would be the only proper muzzle brake for the period of your gun. I don't have a rifle that is screwed up enough to try to install my Cutts, but some day I might find one. It would be neat on a Springfield sporter with a cut barrel.