Gun damage
From: 'Fighting in the air' by Maj. L W B Rees, 1916
"When one sees a machine one is apt to think that hits anywhere will be effective. One is trained to imagine that a small thing, such as a frayed cable, is certain to cause a wreck. Yet machines go up every day and return absolutely under control, but having dozens or even hundreds of holes in different places... The only useful target to really attack is the pilot himself. This target is very small, being of a size about 2 ft by 1 ft 6 inch, and even then shots which hit this target are not certain of putting the Pilot immediately out of action. Therefore, one must concentrate one's attention and one's shooting on this small target, the Pilot, til one has attained one's objective.
If we attack a machine from directly in front or in rear the engine may cover the Pilot's body, or vice versa. This is the minimum target which the machine can present, and any shots hitting the target do damage, but there is a lot of room round the target in which shots which do not actually strike do no damage.
Now, if we imagine a machine being attacked from the side, or straight from above or below. The target which we must aim for still remains the same small one, but now the rounds, which before were non-effective, will hit the engine and Observer, and will become effective... This leads one to suggest that the way to attack is straight at an enemy from above, below or from the side"
From: 'Fighting the S.E.' by Capt. J T B McCudden, 1918
"The position from which a pilot can do most damage to a 2-seater at the least risk to himself and machine, is 100 yards behind it and 50 feet below... I find that it is very difficult to shoot the pilot from directly behind because you probably hit the gunner first, who collapsed in a heap in his cock-pit, and you go on shooting and are simply filling the gunner with lead, and also a huge petrol tank which is usually situated between pilot and gunner, and the pilot gets off without a scratch...
Most 2-seaters will stand a lot of shooting about before giving any evidence of damage ...[but]... one should be very alert when firing at an E.A. at close range, so that, when E.A. falls to pieces, as they very often do, after being fired at a lot, that one does not fly through the wreckage. I narrowly missed flying through a pair of E.A.'s wings recently"
Both extracts are from 'Fighting in the air: the official combat technique instructions for British fighter pilots, 1916-1945' (edited by John Tanner). Arms & Armour Press, 1978 (RAF Museum series, vol.7).
Tracer and explosive
Brock, Buckingham and Pomeroy
(from: http://www.bbc.co.uk/dna/h2g2/A912124)
By the middle of 1916, there were new developments in incendiary/explosive ammunition for .303" machine guns. Initially, there was a reluctance to use them as they contravened the Hague Convention, but Germany's use of gas in April 1915 hardened the resolve to beat the 'Hun' by any means possible. There were three types used together as 'mixed incendiary' the effects of which complemented each other.
Pomeroy
Developed by New Zealand engineer John Pomeroy in 1902, this explosive bullet was quickly adopted by British defence services as a means of combating the growing Zeppelin threat. Filled with nitro-glycerine the bullet ignited the hydrogen gas which escaped from the tear in the Zeppelin gas bag created by the bullet's passage.
Buckingham
The Buckingham bullet (Mk VII bullet) was an incendiary/tracer bullet based on phosphor, invented by James Buckingham in 1914. The bullet contained an incendiary filling which percolated through an annular hole, the seal of which melted on firing, the phosphorus igniting on contact with the air.
Brock
An explosive bullet developed by Commander Frederick Brock RN and first successfully demonstrated in 1915, the Brock bullet was designed to explode between the outer covering and gas cells of an airship. Used by the RFC until 1917 and the RNAS throughout the Great War.
German ammo load
From GERMAN MACHINEGUNS, by Daniel D. Musgrave and Smith Hempstone Oliver, Mor Associates, Wash. D.C, 1971, Chapter III, pp31-49, the Germans used the following cartridges during WW1 for aircraft 7.9 machine guns:
Patrone S, pointed bullet; Patrone Smk pointed with steel core, armor piercing; Patrone SmKL'spur, armor piercing tracer. L'spur=Leuchtspur, means tracer; Patrone PrL, incendiary cartridge developed in 1916 for attacking balloons, the filler was white phosphorus, burns during flight; Patrone SPr, an improved version of the Patrone PrL; Patrone F, armor piercing incendiary bullet. The phosphorus won't burn until the bullet impacts and ruptures the cartridge jacket. The F means Flugzueg (aircraft). This is the one that caused problems with self ignition from the summer heat in July 1918 which caused the life of several German pilots. The ammunition mix in the ammunition belts was: 4 Patrone SmK, 1 Patrone SmKL'spur and later in 1918, 3 Smk, 1 SmKL'spur and 1 Patrone F and this would be repeated throughout the length of the 500 round belt. If incendiary Patrone PrL or the later SPr were used would be loaded in place of 2 of the SmK rounds, thus 2 SmK, 2 Prl or SPr and one SmKL'spur. This belt would be loaded in only one MG for only attacking the balloon. The other gun was loaded for normal air to air combat. There are no explosive bullets listed here.