If you haven’t deprimed the cases yet . The firing pin mark on the primer should be able to tell you which gun shot what brass . If not which gun you should at least be able to separate accordingly. If one chamber is much smaller then the other one set of cases should not chamber in one of the rifles . Those cases are not from custom chamber .
Has anyone brought up press flex/deflection. It seems just about every tread that starts “ I can’t bump my shoulder enough “ really means I’ve not screwed my die in far enough yet . It always blows me away how the first 10 suggestion seem to be grinding something haha . With out first determining if the die and shell holder are actually staying in contact with each other at the top of the stroke .
I was just on another forum discussing this very subject with a guy that says he can’t bump his shoulders back any further even though there was a gap between the die and shell holder at the top of the stroke . I told him to screw the die down further so he did and said there was no change , gap still there and case does not chamber . I then told him to screw it down even further and that he was either going to size his case more or snap his press . Turns out he did both snapped his press in half while attempting to size his case more . That case that he sized while snapping his press finally chambered in his rifle , so it turns out his press was not strong enough to size the case properly . It was a cheap Lee press and he was sizing a larger case so apparently those cast aluminum lee "C" type presses are not that strong lol