Proof designed their AR barrels with the goal of improving performance and reliability in the AR platform. Their Caliber Matched Gas System (CAMGAS) results in a gas system that is tuned specifically for the cartridge and length of the barrel. The AR-15 Platform was originally designed around the 223REM and 5.56NATO cartridges and the AR-10 was designed around the 308 Win/7.62NATO round. With higher performance cartridge such as the 6.5 Creedmoor the bore pressure remains higher further down the barrel.
By moving the port location Proof ensures that the gas system pressure is the same as what the AR platforms were originally designed around. The result is a recoil impulse that is noticeably softer less fouling in the receiver increased reliability of extraction and less wear and tear on brass. This helps keep you on target and shooting while taking advantage of the latest high performance cartridges