XBradTC

When’s the last time you saw an actual P-51D firing actual .50cal machine guns? Well, here’s your chance. Parrothead Jeff sent this along.

You’ll notice not a lot of rounds were actually hitting the target. The best aerial marksmen in the world won’t do well if the guns aren’t “harmonized.” You’d expect the guns in the wing of a fighter to point straight ahead. But in fact, you want them to point inward ever so slightly. Ideally, the stream of fire from all six guns would converge at a point 250 to 300 yards ahead of the fighter. That was typically considered the maximum range a pilot could effectively shoot in aerial combat in World War II. And of course, the idea was to have the greatest possible weight of fire hitting the enemy at once.

The mounts in the wing of fighters allowed both for the guns to be securely and firmly mounted, while also allowing the direction of the gun to be dialed in. The process was straightforward, if rather time consuming. The plane would be placed on the range with the tail elevated as shown, at the distance desired, let’s say 250 yards from the target. Then one by one, each gun would be fired for a very short burst, with the armorers noting the point of impact, then adjusting the guns until they were on target, center mass. After all six guns were adjusted, a final burst would confirm the guns were harmonized.

Each plane had small differences in tolerances, so each plane had to be individually adjusted. However, once the actual adjustments were known (say, for instance, gun #1 needs 4 clicks up and 7 right to be on target) each time the guns were removed for cleaning and reinstalled, the same clicks could be applied. An occasional confirmation firing would suffice to ensure the guns were still harmonized.

Note also that while the Browning .50cal is externally quite similar to the gun used by ground forces, it’s been designed to have a significantly higher rate of fire, about 750rpm, versus 500-550 for the ground version.

Even today, the guns of fighters have to be fired on an actual range to ensure they’re pointed where the pilot thinks they are.