Recently a friend purchased a Browning Automatic Rifle (BAR) in .243 Winchester manufactured in the early 70s.

He is now looking into reloading and asking me to get him started. A question came to mind regarding the choice of propellant(s). Does anyone know or have experience with issues of port pressure being a concern for the BAR? I know of issues regarding military gas-operated rifles, such as the M1 Garand, whereby slow burn rate powder can wreak havoc on the piston and operating rod and wonder if similar restrictions would apply here.

Am looking initially at reloading 70 gr HP.