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When the .303 magazine rifle was introduced to service in 1899 the practice was to proof weapons twice. First the barrel was proofed at an early stage of manufacture with a loose blackpowder charge and separate bullet and then a second time with a conventional proof cartridge when the rifle was finally assembled. Barrels bore the proof marks “1P” and “2P” under a crown to indicate passing these proofs. Since only the second proof used a .303 inch cartridge only those will be discussed here.
Proof Powder
The first cartridge to be introduced was the “Cartridge S.A. .303 Ball Magazine Rifle Proof Powder” which was approved in 1889 but not shown in Lists of changes.
Early production used the case of the Boxer primed ball rounds whilst later production used the Berdan primed case of the Cordite ball rounds. In each case the original ball headstamp was retained. Woolwich records indicate that some were loaded in “contract” cases but only Royal Laboratory ball headstamped ammunition has been seen.
The bullet was highly unusual as it was a long lead paper patched bullet weighing 450 grains that protruded about 60 mm from the case and had to be loaded into the rifle with the bolt removed.
The propellant was 80 grains of black powder in a pellet.
Pressure was 20-21 tons per square inch, only about 10% over the service charge of 70 grains of black powder.
Although cordite ball cartridges were introduced in 1892 the blackpowder proof cartridge continued in use until 1895
Proof Mark I
"Cartridge Proof S.A. Ball .303 inch Cordite Mark I" was approved to design RL 8728 in July 1895 and shown in Lists of Changes Paragraph 21667 "for record" in January 1919. It was also known as"Cartridge S.A. Ball .303 inch Cordite 2nd Proof Mark I".
Early versions used the service Boxer primed case with small primer but later versions used the normal Berdan primed case. The headstamp included the code "PROOF I" and the letter "C" for Cordite and some cases were tinned as an additional identification.
The bullet was the service 215 grain Ball Mark II bullet.
The propellant charge was 35 grains of Cordite Size 3 to give a pressure of 19.6 tsi.
Proof Mark II
When the Cordite Ball Mark VI was introduced in 1904 it gave a slightly higher pressure of between 17 and 18 tsi and so a new proof round was introduced to cater for this.
"Cartridge Proof S.A. ball .303 inch Cordite Mark II" was introduced in 1904 and shown in Lists of Changes Paragraph 21667 "for record" in January 1919. It was declared obsolete in 1929. Canadian production had the case copper washed.
The case was the normal service Berdan case and the headstamp included the code "PROOF II". Depending on date of manufacture it could include the letter "C" for Cordite.
The bullet was the 215 grain Ball Mark VI.
The propellant was 32 grains of Cordite Size 3 to give a pressure of 20 tsi.
Proof Mark III
"Cartridge Proof S.A. Ball .303 inch Cordite Mark III" was approved to design RL 15973 in January 1908 and
shown in Lists of Changes Paragraph 21667 "for record" in January 1919. In 1927 the title was changed to "Cartridge S.A. Proof .303 inch Q Mark III" and the design was changed to DD/L14006.Q3. It was designed for the proof of rifles.
The case was the service Berdan primed case and was copper washed for identification. Prior to 1928 the headstamp included the code "PROOF III" but this was replaced by the code "Q III" ("Q 3" after 1944). Canada continued to include the word "PROOF" in their headstamps during WW2.
Later production had a yellow primer annulus and the caps were sometimes burred in.
The bullet was originally the 215 grain Ball Mark VI but this was later supplemented by the 174 grain Ball Mark VII. By varying the charge weight a constant pressure was obtained.
The propellant with the 215 grain bullet was about 32 grains of Cordite Size 3 and with the 174 grain bullet about 44 grains of Cordite Size 3. The original specification L.9712 (later replaced by L.3031) gave the propellant as Cordite 4 1/2-2. Ordnance Board proceedings of 1941 show the charge for the 215 grain bullet to be 34.5 grains of Cordite Size 3 and for the 174 grain bullet to be 40.6 grains of Cordite MDT 5-2. This reflects the increase in the specified pressure.
The mean pressure was originally set at 24 tsi but as part of the move to make the Q Mark III the common proof round in WW2 this was increased to 25 tsi.
Proof Mark IV
"Cartridge Proof S.A. Ball .303 inch Cordite Mark IV" was approved to design DD/L/2362 circa 1925 but was not shown in Lists of Changes. In December 1927 the title was changed to "Cartridge S.A. Proof .303 inch Q Mark IV".The Proof Mark IV was designed for the proof of automatic weapons..
The case was the service Berdan primed case and was copper washed for identification. Prior to 1928 the headstamp included the code "PROOF IV" but this was replaced by the code "Q IV". Canada continued to include the word "PROOF" in their headstamps during WW2.
Later production had a yellow primer annulus and the caps were sometimes burred in.
The bullet was originally the 215 grain Ball Mark VI but this was later supplemented by the 174 grain Ball Mark VII. By varying the charge weight a constant pressure was obtained.
The propellant with the 215 grain bullet was about 35 grains of Cordite Size 3 and with the 174 grain bullet about 42 grains of Cordite MDT 5-2.
The mean pressure was 26 tsi.
It was decided in June 1941 that a new common proof round for both rifles and automatic weapons would be used and it was intended to develop a new Q Mark V proof round for this purpose. Meanwhile the pressure of the Q Mark III would be increased to 25 tsi and be used with the 174 grain bullet to prove both types of weapon.
The Q mark IV would be allowed to lapse but it was not declared obsolete until March 1963. The Q mark V was never approved although the design was finished.
American Proof WWI
One other proof round exists, made by Winchester Repeating Arms in 1915-16. It is assumed that these were manufactured for proofing the Pattern ’14 rifles being made by Winchester on British contract and that they comply broadly with the contemporary British Proof Mark III.
It is not known when or even if the round was formally approved in Britain, but it would have been some time in 1915. The title of the round is also not known as it was not shown in Lists of Changes either.
The case is a normal Winchester contract Boxer promed case and is tinned all over.The headstamp is "W 15" or "16".
The bullet is the short 174 grain American version of the Mark VII bullet without the aluminium tip.
The propellant is nitro-cellulose and the pressure is presumed to be similar to the British Proof Mark ii at about 24 tsi.
Rifle Grenade Proof Mark I
There was one proof cartridge with a very limited and specific application, and this was to prove the tail tubes of the No.85 anti-tank grenade.
"Cartridge S.A. Rifle Grenade Proof .303 inch QH Mark I" was approved to design DD/L/14006.4 in 1946 but not shown in Lists of Changes.
The case was a normal service case open at the mouth but slightly coned in and closed with a varnished celluloid cup. It was copper washed and according to the drawing the headstamp included the code "QH 1". The primer annulus was yellow.
The propellant was 44 grains of Cordite MDT 5-2 with a guncotton tuft at each end.
It was designed to give a 25% over pressure compared to the Grenade Discharger H Mark IV
It was made in very small numbers and no surviving examples are known, so a copy of the official drawing has been used instead of a photograph.
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