Watch closely as the powder bags are rammed into the powder chamber — the precision of the rammer operator is remarkable. The gun captain signals when to start and stop the ram, and in this video directs a final push of about 2 inches to seat the bags correctly. After the rammer retracts and the spanning tray is removed, the gun captain verifies that the last powder bag is positioned within 6 inches of the mushroom head.
That 6-inch tolerance is critical: the rear of the powder bag carries a red ignition pad, and the primer vent through the mushroom head is only about ¼ inch in diameter and roughly 22 inches long. If the bag is too far forward, the jet of flame from the combination lock primer may not travel far enough to ignite the pad — causing a misfire. If the captain finds the bag too far forward, he reaches into the breech and pulls it back by hand before closing the breech plug.