Don Davie
It is common knowledge that the .303” British rimmed cartridge in various marks was, over a long period of time, the service issue cartridge in Britain and throughout the once-great British Empire. It is perhaps less well known that a number of other cartridges of .303” calibre have been designed and manufactured in Britain and elsewhere.
The identification of the actual calibre of a cartridge cannot always rely upon the nomenclature of the cartridge or the case head-stamp. Also, published bore diameters, cartridge case dimensions and bullet diameters may vary from one source to another – some depend upon manufacturers’ data while others have been determined from the measurement of bores, cases and bullets. Manufacturing tolerances also have an effect. The maximum diameter of a bullet of one calibre may equal or exceed the minimum diameter of a larger calibre. While the diameter of the British .303” service bullet is generally given as .311”, some sources give diameters ranging from .309” to .312”. Case length for the .303” British was 2.151” for the Mk I to Mk VI and 2.211” for the Mk VII and Mk VIII. (Hogg; 24)
This paper identifies some little-known .303” cartridges, including a cartridge that may not have been a .303” as designated, one that may have been a .303” although otherwise designated, and another described as a .303” but certainly not of that calibre.
.303” Swift  A rimmed cartridge of pre-1911 design with a case length of 2.193”. The propellant was 34 grains of Westley Richards Axite and the projectile had a mass of 225 grains and a diameter of .309”. Axite was said to have less erosive and corrosive characteristics than the Cordite propellant customarily used by the British. No performance data is given. (Fleming; 34,35, 207)
.303” Adder (Midrange)  Case length 1.472” - 1.480” and bullet diameter .309” - .312”. A short-range practice cartridge in rimmed form produced by the Birmingham Metal and Munitions Co Ltd pre-1912. The 139 grain projectile was propelled by 13.6 grains of Cordite. As the rim and head dimension were smaller than those of the .303” service cartridge, an adaptor would have been needed to fire this cartridge in .303” service rifles. (Fleming; 36, 37, 208; Hoyem; 142, 213)
.303” Mauser (7.65mm Fraser)  The rimless case of this cartridge was the same as that of the 7.65 x 53 mm Belgian Mauser cartridge, with a length of 2.080” - 2.100”, and the round had a bullet diameter of .311”. The case was stamped 7.65 mm ELEY and was produced for the firm of Daniel Fraser in Edinburgh. Fraser loaded the case with his patented oblique ratchet soft-nose bullet. (Fleming; 30, 31, 206; Hoyem; 144, 213)
.303” Fraser Rimless (.303 Rimless Lee-Enfield)  Case length of this cartridge was 2.201” - 2.203” and bullet diameter is given as .310” - .311”. This case was also produced for Fraser, probably by Eley Brothers, and was loaded by Fraser with his oblique ratchet soft-nose bullet. (Fleming; 30, 31, 206; Hoyem; 144, 213)
.303” Fraser Flanged  Fleming provides an illustration of this cartridge but gives no data. The cartridge was the standard British service .303” case loaded with the Fraser oblique ratchet soft-nose bullet. The propellant was Cordite. (Fleming; 35, 277)
.303” Marksman  This was the British service .303” case loaded with the Eley Marksman bullet over Moddite, an Eley flat strip variation of Cordite, or MDT (modified tubular cordite). The Marksman bullet was a sharp point solid of unknown mass. The cartridge was introduced in Eley’s 1908 catalogue and was still listed in their 1914 catalogue. (Fleming; 34, 277)
.303” Magnum  Produced in both semi-rimmed and rimless forms by W. J. Jeffery, this cartridge was made from at least 1919 to 1932. Case length was 2.342” - 2.353” and bullet diameter was in the range .310” - .311” (Hogg says .312”). Muzzle velocity with a 174-grain projectile was 2850 fps, significantly higher than the 2440 fps of the Mk VII service round with a projectile of the same mass. The cartridge was adopted by the British Match Rifle Committee, and featured in the Kynoch ammunition catalogue until about 1930. Case capacity was similar to that of the 30-06 cartridge but performance was in favour of the British round. (Barnes; 247; Fleming; 38, 39; Hogg; 30: Hoyem;143)
.303” Jeffery Rimless Nitro Express  The case for this cartridge was apparently the .333” Jeffery necked down and reformed and had a length of 2.490 - 2.502”. The .303” Jeffery was possibly an experimental cartridge that was never produced commercially. (Hoyem;  144)
.375”/.303” Westley Richards Accelerated Express (.375”/.303” Axite)  A rimmed cartridge introduced by Westley Richards in about 1906. The cartridge was not a true .303” as the bullet had a diameter of .330”. It did not have a long life, being superseded by the more powerful Westley Richards .318” Rimless Nitro Express cartridge (also with a bullet diameter of .330”) in about 1910. (Barnes; 247; Fleming; 38, 39; Hogg; 28; Hoyem; 138)
.303” Lewis Machine Gun Cartridge  Hoyem states that this was an experimental design developed toward the end of the 1914-1918 War. The cartridge had the same rim diameter and case length as the .303 British service cartridge but a larger case diameter gave increased capacity and improved performance. Adoption of the cartridge would have necessitated the rechambering of the thousands of Lewis LMGs in service and the cartridge was never put into production. (Hoyem; 166)
.303” Enfield Rimless Experimental Cartridge  Tested between 1920 and 1927. Five thousand rounds were produced, loaded with 48.7 grains of nitrocellulose power and either a 174-grain or 200-grain projectile. Case length was 2.21” and bullet diameter was a small .309”. (Hoyem; 165)
.55”/.303” Experimental Anti-Tank Cartridge  This cartridge had a belted case with a length of 3.925” and was loaded with a projectile with a diameter of .312”. No performance data has been found but the cartridge was apparently the Boys .55” Anti-Tank cartridge necked down. (Hogg; 33)
7.65 x 53 mm Mauser  This cartridge was developed by Mauser for the Belgian Pattern 1889 rifle. It was also adopted by Argentina, Bolivia, Columbia, Ecuador, Peru and Turkey for their service rifles. The cartridge and rifles chambered for it are something of a puzzle. There seems to be agreement that land diameter was .301” and bullet diameter .313” but Barnes puts groove diameter as .311” for the Argentinian and Turkish rifles and .314” for the Belgian rifle. While groove diameter of .311” indicates a bullet similar to the .303”, the stated bullet diameter of .313” suggests otherwise. (Barnes; 221, 236; Hogg; 28, 29)
7.7 X 58 mm Arisaka  Introduced for the Arisaka Model 99 rifle in 1939, this cartridge had a projectile with a diameter of .311”. The 7.7 x 58 mm case had similar dimensions to the .303” British cartridge but was of rimless design. The British and Japanese cartridges produced much the same ballistics and generated similar pressures. Semi-rimmed and rimmed versions of this cartridge were also produced for use in Japanese light and medium machine guns. (Barnes; 219)
.303” Savage  Designed in 1895 as a potential military cartridge and manufactured to about 1945, this rimmed cartridge was produced in the United States for the Savage Model 99 rifle. Barnes states that it was misnamed, as it was a .30” calibre cartridge with a bullet diameter of .308”. However, Hogg notes that bullet diameter of 311” was accepted by the International Standards Organization as standard for this cartridge, and that would make it a .303”. (Barnes; 60; Hogg; 15, 24)
.30” US Experimental Cartridge  With a rimless case of 3.350” and a .311” projectile this cartridge was of about 1912 vintage. No performance data has been found.  On the basis of bullet diameter, the cartridge could properly be considered a .303”. (Hogg; 29)
Much has been written about the .303” British service round but there is a dearth of information on other .303”s. Apparently, the sporting and match cartridges listed above did not have sufficient merit to justify their continued manufacture, although the .303” Magnum at least appears to have been an excellent cartridge. Similarly, the experimental service cartridges did not gain acceptance and the .303” Mk VII cartridge remained the service standard until the adoption of the SLR in 7.62 x 51 mm calibre.
 If you have any further information on the cartridges considered above, or knowledge of other .303” cartridge designs, your input or advice would be most welcome!
Barnes, F. C., (ed. K. Warner), Cartridges of the World (5th Edition), Northbrook, DBI Books, Inc., 1985.
Fleming, B., British Sporting Rifle Cartridges, Oceanside, Armory Publications, 1998.
Hogg, I. V., The Cartridge Guide, Melbourne, Arms and Armour Press, 1982.
Hoyem, G. A., The History and Development of Small Arms Ammunition, Vol. 3, British Sporting Rifle, Tacoma, Armory Publications, 1985.