12boreman, it is as Mike stated, do you know the bore size? I am helping a friend who owns quite a few 4 bores and all of his seem to be around .930-.935. He does have a Scott that has larger bores and they seem to be about .950-.960 (haven't pinpointed it as of yet)
Back at this time of the 4 bore, every maker seemed to use what he thought was good.

My friend contacted the Birmingham Proof House and they said 1.050, but from my research that is for muzzle loading guns, not breech openers.

David