The bolt face has been opened up to something bigger than a 375 H&H, and just a hair too small for a 404 Jeffery. Im taking a WAG that it was built by Hoffman Arms into either a 280 Jeffery or a 333 Jeffery as the action is standard length. Might have to go with a 333 Jeffery with a .338 diameter bore when I get it barreled.