If you said what you meant and meant what you said (" ... a .300 super magnum loaded at 55,000 psi burns out barrels faster than a .308 loaded to 60,000 psi."), you got it exactly backward. It's HIGH PRESSURE and its related high temperature that burns-out barrels faster. So the smaller cartridge loaded to a higher pressure burns barrels out faster than the larger cartridge loaded to a lower pressure.
