Thanks Gunman1911.
I have looked up the pressures and have read both pro and con articles on the net.
The Con is as you state due to chamber pressure. The pro side says that "Yes, NATO ammo runs around 50,000 and .308 runs around 60,000 but the chambers were proofed at those (higher) levels when manufactured."
So you see where I am on this. I was hoping some one here had proof of the chamber being proofed originally at higher levels or some definitive answer.