WWII aircraft

Planes with wing mounted guns: how far forward of the plane centerline were they trained to intersect? I’m curious if this fluctuated a lot per country/manufacturer?

Also, what kind of maintenance took place, on average? Were the barrels cleaned regularly?

I know that at least in the case of some units flying the P-51, the bullet flight path and interception points were adjustable and up to the pilot’s discretion. If the pilot wanted one pair to intersect at 150 yards, one pair at 200 yards and one pair at 250 yards then fair enough. His plane, his choice.

It’s conceivable that there may have been a “standard” setting for the weapon aiming and that different units followed to the standards to different degrees.

I’m sure the barrels and mechanisms were thoroughly cleaned between mission.

I agree with Alpha Twit.

How much of a difference would it make? The pilots were firing multiple machine guns from a very maneuverable airplane that was bouncing in the air, usually at another very maneuverable plane that was also bouncing through the air. It’s not like they were sharpshooters aiming at a fixed target.

I seem to recall that the Army Air Corps convinced the US army that wing mounted guns were as accurate as line of sight guns back in the '30s. Could one safely assume that precise aim was less important than getting a lot of shells into the general area of the target (and possibly aiming by the tracers)?

Thanks all.

I am more curious about how the plane left the assembly line; was the aiming set there or in the field?

Convergence was set in the field, by the ground crew. The normal-ish range was 300 yards or so for U.S. planes, a little shorter for the P-51, since the guns were closer together. British planes used 400 yards, and being Brits, didn’t allow their pilots to change the settings for a while. They were set at 400 to hit bombers, which were bigger targets, and IIRC it was only changed when Germany started sending fighters over the English Channel.

There was no reason to set pairs of guns to converge at different ranges.

Pilots in the Pacific who were doing a lot of ground attack would set the convergence to infinity, which is better for strafing.

Convergence is important, because aerial gunnery is very difficult, and most aircraft only had a few seconds worth of ammo on board. Therefore, the idea was to set the gunsights to the convergence range so that when you took a shot, you put all the bullets into as small an area as possible, maximizing damage from a hit. There was no spray n’ pray. Some planes would use a “box” convergence, but most used a point that all the guns were aimed at.

When we started using gyro gunsights, convergence was often set out a bit farther, because longer range hits were possible.

As far as maintenance goes, I’m sure they occasionally cleaned the guns, but I doubt they broke them down and reassembled them every flight cycle.

At he beginning of WII the RAF harmonised their fighter machine guns at 400 yards (“the Dowding spread”). This was designed for attacking bombers and was not found suitable for dogfights where a better result was obtained by coming in closer before opening fire. Individual squadrons and pilots soon harmonised their guns to 200 yards or so.

So yes, convergence distance had its value in accuracy, and yes, pilots could get their fitters to adjust the same.

Information from “Piece of Cake”, by Derek Robinson, fiction,and “Fighter Pilot” by Paul Richey, non-fiction.

You couldn’t be more wrong :).
Accuracy and sharpshooting was paramount, and while it was indeed quite difficult to hit a target zooming 90° from your path, esp. with the limited training and primitive sights, those pilots who managed to survive long enough to get the knack of it were the most wanted, and probably those who lived the longest too.
This because on-board ammo stores were extremely short. Each machine gun or cannon carried around 500-1000 rounds (barring huge flying fortresses and special planes) which amounts to half, maybe a full minute of sustained firing tops. Spraying and praying was not an option.

Ignorance fought. Thanks!