.45 inch
The .45 inch cartridges described in this section were intended to be fired either from carbines or Maxim machine guns.
There were two types of .45 inch cartridges in British service, the .45 inch Martini Henry (M-H) and the .45 inch Gardner Gatling (G.G.). Unless otherwise stated, the rounds described below were loaded in both case types, the bullets being identical.
.45 inch Martini-Henry Royal Laboratory Flaming Bullet
Even before the outbreak of war in 1914 The War Office were well aware of the potential dangers posed by Zeppelins and as early as 1913 had considered the use of explosive or incendiary bullets to successfully ignite gas. They also realised that the .303 inch bullet would be unlikely to carry enough incendiary mix so turned their attention to the .577/.450 inch Martini Henry cartridge to be fired from Martini carbines.
"Cartridge S.A. Incendiary .45 inch Mark I" was approved to design RL 21404A(1) and shown in Lists of Changes Paragraph 17122 dated December 1914. In 1916, although by then obsolescent, the title was changed to "Cartridge S.A. Tracer Martini Henry Rifle and Machine Gun Mark I". It was more commonly referred to as the "RL Incendiary" or "Flaming bullet".
The case was solid drawn brass and was obtained from broken down ball rounds. The headstamp was that of the original ball round and some were loaded in cases carrying the Indian government ownership stamp.
The original bullet was round nosed brass but by August 1914 this had been replaced by a more streamlined pointed bullet.
The bullet consisted of a heavy brass envelope with two raised bands and one cannelure at the rear. It had no core, the filling being the incendiary composition with the envelope closed by a threaded brass plug with a central hole. The filling was about 50 grains of a mixture of 20 parts potassium perchloride and 7 parts aluminium, pressed into the envelope at a pressure of 11.4 tons per square inch. On top of this was 20 grains of an igniting mixture of barium thermite and copper.
The bullet weighed 270 grains and there was a small hole drilled in the nose.
After trials the design of the bullet was slightly modified by reducing the loading pressure to 10 tsi and replacing the brass closing plug with one made of steel.
The propellant was about 47 grains of Cordite size 3 and muzzle velocity was estimated at 2,150 fps.
Left to right: original Round nosed bullet, service bullet and base showing closing plug and aperture.
Other slightly different versions of the bullet exist, but these may be purely experimental. One has no nose hole drilled and has a thicker steel closing plug whilst the other has a single longer raised "driving band" and again no nose hole.
.45 inch SPG Tracer
In 1916 .45 inch SPG tracer was loaded in both Martini and G.G. cases.
Two different types of bullet were loaded, externally identical but differing in internal construction. Both types were semi-pointed with a thick cupro-nickel envelope and no core, the tracer and priming composition being pressed directly into the envelope. The bullets had no cannelure or base plug. The first type had a wooden nose plug 11-14mm long with the tracer composition pressed behind it and weighed 290 grains.
The second type had no nose plug and weighed 295 grains, of which 91 grains was tracer composition.
Propellant weight in M-H cases was between 40 and 55 grains and velocity was about 2,000 fps.
When loaded into M-H cases the bullet was seated quite deep, giving an overall cartridge length of 78mm.
M-H case tracer G.G. case tracer
.45 inch Armour Piercing
Armour piercing bullets were loaded in both M-H and G.G. cases, and two types of bullet are known.
One type, loaded in a G.G. case, has an envelope of copper or gilding metal and appears to be a scaled up version of the .303 inch Mark VIIP bullet. An X-ray seems to confirm this as it shows a lead sheath around the steel core. The envelope is believed to be the subject of Kynoch drawing BJ2/16A dated October 1917.
The case is that of a Cordite Ball Mark I with the headstamp "R/|\L C I" with the letter "P" overstamped, further confirmation that it is based on the .303 inch bullet. Bullet weight is 355 grains.
The second type, also loaded into a G.G. case is longer and heavier with a cupro-nickel envelope. this also shows a lead sleeve around the steel core when X-rayed. Bullet weight id 483 grains.
Left: Second type AP bullet loaded in a G.G. case.