New member - basis questions

Harold said:

* Is there a general rule as to which type of gun (machine gun or cannon) would be mounted in a fixed position and which type would be able to swivel? I know a machine gun would have to be able to pivot. Otherwise the pilot would seem to be very limited as to when he could shoot.

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Early in WWl, several aircraft were armed with a gunner in front of a pusher (propeller in the rear) who could swivel a machine gun. A Frenchman by the name of Roland Garros (I suspect the same person the French tennis stadium is named after) fixed a forward firing gun on his tractor aircraft (propeller in front), mounted a deflecting steel plate to protect the propeller (which wasn't 100% successful) and soon demonstrated that aiming the aircraft, with shot down Germans, was a superior design. Add to this Anthony Fokkers syncronization gear on the propeller (interrupting the machine gun when the prop is in the way. Which was inspired by Garros aircraft after he shot himself down) on his German Eindecker fighter, and history was made. Since that time, nearly all fighters have had their primary machine gun armament fixed along the centerline of the aircraft. Wing mounted guns were aimed to converge at some selected point or points.

spike_jones said:

Sorry, not sure this is relevent to the thread but not sure where to post this but when diving in the English Channel last year I found a spent 20mm cartridge case. Stamped on the base is "43" and "W R A".
The case height is 100mm. I'ts ejector slot is indented on the case.

I presume this is an aircraft cannon but can anyone help to identify it further?

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Are you sure its 20mm? It looks like a .50 Browning case to me.

It is much too long for an MG 151/20 case (82mm long) and too short for a 20mm Hispano (110mm).

Measure the diameter of the base. If it's around 20mm it's definitely a .50 BMG.

Tony Williams: Military gun and ammunition website and discussion forum

Thanks for the reply.

As far as I can accurately it's definately 20mm and no more in diameter.

So if it's a BMG, would that be an aircraft gun or ship?

Cheers

spike_jones said:

So if it's a BMG, would that be an aircraft gun or ship?

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It's hard to say, since the same ammo was used in both. The RN did have a few .50 BMGs, and some later Spitfires as well as nearly all USAAF planes had the .50 as well.

It may depend on where in the Channel it was found. The further east, the more likely it is to be from an aircraft.

Tony Williams: Military gun and ammunition website and discussion forum

Hi agian,

Excuse my ignorance, but I thought a 0.50 cal BMG cartridge was 12.7mm in diameter?

USA 0.50"/90 (12.7 mm) M2 Browning Machine Gun (BMG)

Cheers

oops, or is the 12.7mm the diameter of the actual projectile?

The projectile. With 20mm he is talking about the casing.