If I understand you right then you are really not talking about the chamber being oversized but having a long throat?

I don't shoot 140 eldm bullets but you can't guarantee you have a long throat just because 1 bullet puts you over the max case length to get to the lands.... long sleek high bc bullets do that- which is why they make custom reamers. That production gun needs to also be able to chamber the round nose hunting bullets out to sammi length.

I didn't even bother measuring the distance to the lands on my last gun during load development. You could tell the bullet was not in the lands- and it needed to be mag length so it would have been pointless to measure. Being close to the lands is overrated (with a few exceptions)- and you can usually find a load or bullet that will take the jump.