The seller has 30-06 on the tag, so I assume that is what it is chambered for, or he does not know any better. It is a very early rifle, at that time I believe G&H was still assigning blocks of numbers to a specific caliber, and I believe the 400 block was for 30-06, but I do not have Michael's book handy to check that. It sure looks for all the world to me like an armory NRA sporter barrel. Neat rifle, but I can't imagine what the barrel markings would indicate.

John