mbatten,
I have a set of 450- 3 1/4" dies, if you send me a case that will not chamber, I will size it in my die and send it back to you. If it chambers then, we can decide what to do. I don't especially want to get rid of the dies but would be open to sizing a reasonable number of cases for you. If it works, I agree with Bill that the dies you have should work after you fireform them in your rifle. His idea of the tape may work also, you can wrap the case with paper or file label and tap it into the chamber with a hammer( padded by a wood block)(oil the paper) and drive it out with a dowel. Before going through all this, you can smoke the case or blacken it with a felt tip marker, then push it into the chamber as far as you can. This should show where the interference is. You might also check to insure the rim isn't too thick( put it in, upside down and see if it the rim sits "proud" of the rim recess).
Mike
