I have been trying to do some research on a few top British maker .577 NE double rifles that were built around 1903 and the barrel flats are stamped:
.577 EX
90 Cordite - 650 Max

These are .577 NE 3 inch guns and I take they are regulated/proofed for the 90 gr Cordite / 650 gr Bullet load. How does this load compare to the full bore 750 gr loads? Is it anemic and not as useful as a dangerous game "stopper" rifle? I assume that shooting full bore loads would not be safe in these rifles, regardless of regulation?

Thanks!