The main problem is right now I can't shoot the gun. I will do some more investigating. 500 nitro, you are correct, the problem is the gun won't chamber, because the bolt will not close all the way. I was under the impression from the previous owner that the brass was factory brass. I guess the shoulder could be in the wrong place, it measures to spec though. Thanks for the comments guys, I'll let you know how things turn out on this gun.