I bought some Jamison cartridges and fired a handful. Either the rims are out of round, or, the little alignment/catch projection on the bolt face needs a tiny bevel. I had to rotate some of the cartridges so the bolt would close properly. Upon firing, the brass definitely expanded. I figured there would be some resistance with the Legacy sizing die, but there wasn't. The brass did not appear to have been FL sized at all. They dropped right into the chamber, though, which was nice. At least the brass will not be overworked. I have some .515" bullets on the way. Cimarron should change their bore/groove spec sheet for the benefit of the uninformed. Cheers!