You have to drill the port, springs will not do it. Drill only 1 of the 2 ports. You should gradually increase the drill size until the gun functions with the loads you want to use. I think it will take about a 1/8 drill. You will need extended length bits, and reach the ports through the hole in the ring attached to the barrel. A magnum barrel is set up for 3" magnum shells, but will usually work with 2 3/4 magnum shells, but not lower power shells. Once you drill a port you should not shoot 3" shells. As an alternative you can find a 2 3/4
barrel. Barrels from Al1, al2, 301, 302,303 and browning b80 will interchange. Barrels from 390 and later guns will not. Even 2 3/4 barrels may need a port opened to work reliably with low power 2 3/4 shells. The early guns were set up for relatively hot Italian loads.