Gun Jams.

[Ginger.]

Looking through "High in the empty Blue" I was suprised at the number of jams on their early patrols.They happened to sprogs and veterans alike, and I wondered why.The groundcrews were good men and both the Vickers and Lewis guns had been in use for ages on aircraft.If it turns out this ammount of jamming was normal my admiration for WW1 birdmen will go up even more.I'd not think anyone as sneaky as the Huns would not find a solution to the problem,or did they have the same problems?.

Gun jams were common on both sides. There were a large number of reasons for these problems, so solutions were not simple, although improvements were of course made throughout the war. Here's some of the reasons that I'm familiar with:

-Inferior quality of ammunition: quality control was poor during manufacturing. Casings could be slightly off-size, primers set too deep or not deep enough, etc. Many pilots hand-picked their bullets; later in the war this kind of quality control was SOP for the gunnery sergeant and his underlings for the entire squadron.

-Problems due to temperature extremes: Lubricants for the guns and bullets that worked fine at ground level solidified at altitude, where the temperature might be -40 F. Since the guns had to work through a wide range of temperatures in a single flight, this posed a serious problem. Temperature extremes could result in jams in the feeding or extraction of cartridges, broken firing pins and other mechanical components, and so on. It was common for spare parts for the guns to be carried on board. It was also common for pilots and observers to fire their guns regularly once at altitude in an effort to keep them warm. On the other hand, firing long bursts could result in jams through overheating. Most pilots restricted their bursts to no more than three or four seconds.

Machine-gun belts: Initially, Vickers and Spandau guns used the standard leather belts to hold cartridges. Again, this material was not reliable in the cold and was sensitive to the manner in which the cartridges were inserted into the belt; that is, the depth to which the cartridge was placed in the belt. Disintegrating link belts resolved this problem later in the war.

Lewis gun pans: The rotating single or double-drum ammunition pan used on the Lewis gun was not intended for aircraft. If fired during a dive or other maneuver, the weight of the drum could cause it to shift out of alignment and jams would result.

Mixtures of bullet types: Feeding problems could result from the combination of ball, tracer, Buckingham and Brock ammunition commonly used, which did not all have the same characteristics or shapes.

[Shooter]

Another problem was the fact that all machine guns at the time depended upon gravity for their feeding systems to work. Most still do.

During ACM activities, zero-gee conditions would occur that would jam up weapons. Firing while inverted also tended to cause jams.

Don't know about disintegrating metallic link belts, though. US and UK machine guns were still using cloth belts during part the Second Big Show (at least the ground guys were). Maybe someone has some more info on that.

Shooter sends

The Vickers gun was found to have a rather violent closing action, due to the strength of the recoil spring. Barrel chambers were, therefore, chambered .004" short. It was found that the cartridges reformed in the chambers and allowed the gun to go completely into battery. When chambers were reamed that allowed the action to close on the "go" gage, it was found that inertia caused an excess headspace of .004", which allowed the fired cartridge to cling to the chamber at the neck and stretch backward to the bolt face; this caused case separations that constituted a class 3 jam that could not be cleared in the air.
In a dive, the effect of gravity feed was lessened as the angle of the dive. The Lewis gun had undersized parts that commonly failed.

[stevedrew]

Ginger,
There is a chapter in the magnificent book "Naval Eight", (edited by E.G.Johnstone, Arms and Armour Press), that is written by, and describes fully the duties of an Armament Officer. It is written by the Armament Officer for Naval Eight Squadron, Captain D. W. Pinkney, MBE.
There can be no better a description of the frustrations of the Armament Officer, being unable to find intermittent faults because the problems only occurred in the air, and cleared themselves by the time the pilot landed.
I quote from this chapter:
"For the umpteenth time, I sat down and made a list of possibilities which might be the cause of the trouble. I took a spare gun and criminally assaulted it. I filed its gear out of shape, altered the spring tension, mixed tracer ammunition with the ordinary, altered the angle of the parts of the lock, and ill-used it in other ways which amounted to assault and battery on Messrs. Vickers' good name. Between each experiment I tried the gun, and it fired perfectly. The gun will, in fact, stand an astonishing amount of abuse without packing up.
And then one day when things were reaching breaking point, a pair of the defaulting guns arrived back on the aerodrome, the pilot having missed a sitting Hun. I climbed on to the machine, complete with dental mirror and a high blood-pressure induced by supressed blasphemy. Nothing apparently wrong, until I shoved the mirror down one of the chutes through which the wonderful new disintegrating aluminium belt links were supposed to escape, and saw two of them fixed in a loving embrace right across the fairway. The mystery was solved. As the machine dived, an air eddy was formed at the exit of the chute, and the links being very light got held up, then finally mixed in a tight mass, and very soon stopped the firing. Usually as the machines returned home the links had cleared themselves, and by the time it got back the chute was free again. I got Jordan to prove this for me, and he succeeded in getting back from a trial flight with one chute completely full of jambed links...A slight alteration to the shape and angle of the chute completely cured the trouble, and left everything nice and clear for the "next please"."

The book details most of the types of jambs that occured, and how they got around to solving it. There is also a big "thanks" to the pilots of Naval Eight, who NEVER complained their guns had jambed, merely reporting the fact to the Armaments Officer on his return. It must have made his very difficult job a hell of a lot easier.

Steve Drew

C&C NO1 2000 has an article on 213 Squadron in which Collishaw is quoted describing an engagement in which it became apparent that the majority of guns on both sides had jammed due to freezing conditions.

andy