.303 inch Armour Piercing
In the years preceding World War One the War Office had experimented with a .303 inch armour piercing bullet based on a design by George Roth of Austria which had given encouraging results against steel plate, but gave less penetration against deal planks than the standard Mark VI ball bullet. The Roth design was semi-round nosed and constructed in what was to later become the standard pattern, a steel core surrounded by a lead sleeve within a normal envelope
No further action seems to have been taken, but once the war stagnated into static trench warfare at the end of 1914 there were demands from the British Expeditionary Force for armour piercing rounds to defeat German sniper plates and field gun shields.
Armour Piercing Mark VIIS
"Cartridge S.A. Ball .303 inch Mark VII.S" was approved to design RL 23034/1 in December 1915 but not shown in Lists of Changes until LoC Paragraph 19945 in February 1918. Originally it was intended that the title should be "Mark VII*" but this was
objected to on the grounds that it would draw unnecessary attention, as was the plan to advance it to Mark VIII. The Mark VIIS was based on the normal Mark VII ball bullet but with the aluminium tip replaced by one of steel.
The case was the normal Berdan primed ball case with 0.6 grains of cap composition. The headstamp was to include the code "S", but many had a normal ball headstamp and can thus be only identified once out of the packet by the magnetic attraction of the bullet tip.
The bullet had a cupro-nickel envelope with a lead antimony rear core and a steel tip weighing 33 grains. Total bullet weight was 174 grains. The bullet had a single cannelure and was secured in the casse by the usual three indents.
The propellant was 37.5 grains of Cordite MDT 5-2 with one glazeboard wad.
Velocity was about 2,380 fps.
Armour Piercing Mark VIIP
The Mark VIIS was not very successful and was soon replaced by a Kynoch design
"Cartridge S.A. Ball .303 inch Mark VIIP" was approved to design IDW 3830 (based on Kynoch design 38/137) in November 1916
but was not shown in Lists of Changes. A nitro-cellulose version, "Cartridge S.A. Ball .303 inch Mark VIIP.z" was approved to design RL 26899 in September 1918.
The case was the normal Berdan primed ball case with 0.6 grains of cap composition. Early production had the headstamp "K.A.P." but the normal headstamp included the code "P" or "PZ". In 1918 it was authorised to have a green primer annulus.
The bullet had a cupro-nickel envelope with a heeled steel core enclosed in a lead sleeve. The bullet weight was 174 grains and it officially had one cannelure, but specimens often have none. The bullet was secured in the case by three indents.
The propellant was 37.5 grains of Cordite MDT 5-2 with one glazeboard wad or 43 grains of nitro-cellulose.
This very poor photocopy shows the label of a box of Mark VIIP labelled "SPECIALLY SELECTED FOR SNIPERS"
.Armour Piercing Mark VIIF
The Mark VIIF was based on the French 8mm Lebel armour piercing bullet and was developed and made by Kings Norton Metal Co.
"Cartridge S.A. Ball .303 inch Mark VIIF" was approved in August 1916 and the nitro-cellulose version "Cartridge S.A. Ball .303 inch Mark VIIF.z" in September 1917. Both were shown in LoC Paragraph 19945 dated February 1918.
The case was the normal Berdan primed ball case with 0.6 grains of cap composition and the headstamp included the code "F" or "FZ". A green primer annulus was approved in 1918 but the Mark VIIF was no longer being manufactured by then.
The bullet was made from solid copper rod, bored out to receive a steel core weighing 65 to 70 grains. Total bullet weight was 155 grains and it was secured in the case by coning.
Propellant was 40 grains of Cordite MDT 5-2 with one wad or 40 grains of nitro-cellulose.
Velocity was about 2,450 fps.
For proof, 60% of bullets had to penetrate a 8mm plate at 175 yards and 80% had to penetrate a 7mm plate at 300 yards. The Mark VIIF was considered semi-armour piercing and in 1928 "F" became the code in general use to denote this class of ammunition, irrespective of calibre.
Armour Piercing Mark VIIW
The army in France was demanding a better armour piercing bullet in 1917 and so an improved version of the Mark VIIP with a heavier core was developed by Woolwich.
"Cartridge S.A. Ball .303 inch NC Mark VIIW.z" was approved to design RL 26918 in November 1917 and shown in LoC Paragraph 21354 dated November 1918. A Cordite version, "Cartridge S.A. Ball .303 inch Mark VIIW" was approved later. In 1927 the title was changed to "Cartridge S.A. Armour Piercing .303 inch W Mark I" (or "W Mark Iz") and the original design was superseded by DD/L/3879 in 1928 and DD/L/5906 for RAF "Red Label" ammunition.
The case was the normal Berdan primed ball case with 0.6 grains of cap composition and the headstamp included the code "VIIW" or "VIIWZ" until the end of 1927 and occassionally afterwards. Often in WWI the nitro-cellulose loaded rounds did not include the "Z" in the headstamp. A green primer annulus was approved in April 1918 and some production had the caps secured by burring. From 1928 the headstamp included the code "WI" or "WIZ".
The bullet had an envelope of cupro-nickel clad steel or gilding metal clad steel with a steel core in a lead sheath. It had one cannelure and weighed 174 grains, the core weighing 93 grains. the portion within the case was coated with beeswax or the case neck varnished.
Propellant was 37 grains of Cordite MDT 5-2 with one wad or 43 grains of nitro-cellulose.
Velocity was about 2,500 fps at a pressure of about 20.5 tsi..
For proof, 70% of bullets had to penetrate a 10mm plate at 100 yards range.
Post war contracts:
Kynoch produced a great deal of .303 inch armour piercing ammunition on contract for foreign governments, often headstamped "WIIW" right up to WW2. In 1948 they manufactured a contract for the Argentine Air Force which was headstamped "WIZ" and had a light green bullet tip.
Left: Packet label for 1948 Kynoch W Mark Iz cartridges used as Provisional Standards.
Armour Piercing W Mark I India Pattern
One other mark of armour piercing was approved in India. This was the "Cartridge S.A. Armour Piercing .303 inch W Mark I, India Pattern" and was approved to Design IA.88 sometime in 1941.
The case was that of the normal .303 inch with a green cap annulus. The headstamp included the code "WI.I.P."
The bullet weighed 158 grains and differed from the normal W Mark Iz in having no lead sheath between the envelope and the core. There was a small lead plug at the base of the bullet securing the core.
Propellant was 39.5 grains of MDT 5-2 Cordite with one wad to give a velocity of about 2,500 fps.
The above data is based on information in "Ammunition Pamphlet (India) S.A.A. No.1" published by Kirkee Arsenal, 1945.
Drawing of the W Mark I IP from the above pamphlet.
Semi-Armour Piercing F Mark I
In 1941 a batch of steel in South Africa intended to be made into cores for W Mark I armour piercing ammunition at Pretoria was found to be unsuitable for final hardeneing and could not meet the W Mark I specification. Rather than waste the components, it was decided to utilise them as semi-armour piercing.
"Cartridge S.A. Semi-Armour Piercing .303 inch F Mark I" was introduced in 1941 and only a single batch was made.
The cases were headstamped "U 1941 FI" and had a green primer annulus.
The bullet had a gilding metal clad envelope with the core in a lead sheath, as in the W Mark I and weighed 174 grains.