Vickers Machine Gun

Hello all.

Here is a technical question that I hope someone can answer. When one speaks of an aircraft being armed with twin Vickers machine guns, it seems to me that there were in fact two separate machine guns mounted on the aircraft but connected to a single firing mechanism.

One often reads of machine guns jamming during combat with the result that the pilot abandons the fight. If the so-called twin Vickers were as I have surmised two separate guns connected to the same firing mechanism, does that mean that both guns have jammed simultaneously? How likely was a double jam? Presumably if just one gun jammed, the pilot would continue to pursue his prey with that single weapon.

Am I wrong in my assumption? Was a so-called twin Vickers in fact two barrels connected to and sharing a single feeding, firing and extractor mechanism?

Cheers

[R Pope]

They were completely separate, sharing only a common triggering device. If one jammed, the other still worked.

[ww1 ace]

Right on R Pope!

Every machinegun has it's own action, barrel and feed mechanism.
If the two guns are mounted to fire through the arc of a single propeller they must have an interrupter or a synchronizng mechanism. This is usually supplied by the engine. Since there is only one engine there can only be one interrupter/synchronizer mechanism. If this fails both guns stop or the propeller is shot off.
But the most common stoppages are from loading/unloading errors. Overlength rounds, spent hulls that are not extracted and jamming caused by the metal belts that some guns used.
Pilots could normaly only operate the bolt of the offending gun but I read that some enterprising pilots carried homemade tools to try and extract the offending piece of metal.
Charlie

(British soldiers are) "lions led by donkeys".
Gen. Ludendorf

[TonyWilliams]

Extracts from 'Flying Guns - World War 1: Development of Aircraft Guns, Ammunition and Installations 1914-33':

"Reliability was a significant problem in First World War aircraft guns, and the main cause of failure was poor quality ammunition. In the British 'Handbook of Aircraft Armament', the notes on the Lewis gun contain the following:

Examination of Ammunition

Every round should be carefully looked over for dents, deepset caps, defective bullets, split cases &c., before it is placed in the magazine.
The best service test applicable to discover defects in shape is to use a spare Lewis gun barrel and drop each round into it in order to see that the cartridge enters freely. The rims should be examined to see that, as far as possibly by eye, they are not too thick.

Several cases have been discovered in England of the cartridge containing insufficient or no charge, so that it would be convenient if the N.C.O. or man in charge of guns were able to test the comparative weight of each cartridge with a good one.

If possible U.S. ammunition should not be used as it has been found defective in various respects at this school."

and:

"A major contributor to synchronisation problems (and gun reliability generally) was ammunition quality, which tended to be variable during the War. Pilots frequently carried a mallet with which to hammer the loading lever in order to chamber a recalcitrant cartridge. In an attempt to resolve this, the British introduced in 1917 "Green Label" (or "Green Cross") .303 in ball ammunition specifically for synchronised guns. This was taken from standard production lines, but carefully selected from batches which complied with tighter manufacturing tolerances and gave reliable ignition. This proved successful and was followed up in 1918 by establishing special production lines to make high quality ammunition for this purpose. This was known as "Red Label" (also as "Special for RAF, Red Label", "Special for RAF" and finally "Special") and ball, AP and SPG tracer ammunition were produced."

Tony Williams: Military gun and ammunition website and Discussion forum

Thanks chaps.

Does anyone have a diagram or can anyone point me in the right internet direction to get a detailed diagram of the set up of the twin Vickers on a Camel (or Snipe, or Dolphin)? In particular, I would like to know more about the firing mechanism for the guns.

A diagram breaking the Vickers down into its component parts would also be helpful.