THE .5" VICKERS GUNS
Anthony G Williams
The story of the Vickers gun is well known. It originated in the first successful self-powered machine gun, the Maxim of 1884, which had become the standard machine gun of the British Army by 1891 and was adopted (under various names) by many other armies. A modified version with a more compact mechanism was adopted by the British Army early in the 20th Century as the Vickers-Maxim but later simply became known as the Vickers. It was available for various rifle cartridges (up to .45" or 11.5mm) but in British service was overwhelmingly used in .303" (7.7x56R) calibre. It fought through two world wars and remained in front-line British service until the mid-1950s.
Also well known are the big "pom-poms" in 37mm or 40mm. The first of these was the Maxim one-pounder (1pdr) of the late 19th Century in 37x94R calibre, named for the weight of the shell. This was manufactured by Vickers, who went on to develop both lighter (1pdr MkIII, in 37x69R) and heavier versions. The first of the latter was the 1½pdr (37x123R) just before the First World War, but shortly afterwards this was replaced by the 2pdr (40x158R) which became the standard naval AA gun, available in single, four and eight-barrel mountings, serving until after the Second World War.
In between these were the .5" machine guns, which are much less well known. This account is intended to describe the various experimental and service weapons developed in the interwar period, some of which saw service but several of which did not.
The origin of the .5" Vickers goes back to the First World War. It seems that two or three different problems prompted the development of this gun. One was the need to fire bullets large enough to carry a useful incendiary charge to set light to enemy balloons and airships. Some of the rifle-calibre Vickers had been chambered for obsolete rifle cartridges such as the 11mm Gras in order to achieve this, but a purpose-designed modern cartridge would obviously be better. The second was the need for a more hard-hitting machine gun against aircraft, some of which were now being fitted with armour. The third was the development of the tank.
Although the German 13mm Mauser M1918 anti-tank rifle and the associated TuF (Tank under Flieger, after the intended targets) heavy machine gun are now famous, the parallel British developments are not. These were based around a .600/.500" cartridge originally derived from an elephant gun round. The anti-tank rifle was the Godsal of 1918, the machine gun was a Vickers. The Godsal disappeared from the scene (although an example exists in the MoD Pattern Room) but the cartridge for the machine gun went through various evolutions (included a version with a belted case) until the final form emerged in 1921. This used a rimless 12.7x81mm case and was known by Vickers as the .5V.580, after the bullet weight in grains (37.5 grams). The ammunition was officially adopted for service in 1924.
The new Vickers .5" was offered in three different versions for the three services. The army gun was water-cooled and fired at 450 rpm. The naval version was similar in appearance but had the rate of fire boosted to 700 rpm. The air-force version combined the 700 rpm rate of fire with an air-cooled barrel.
The Aircraft Guns
During the 1920s the RAF tested the .5" Vickers in comparison with the M1924 version of the .5" Browning gun. The results were inconclusive; the Browning was more powerful (it fired a bigger, 12.7x99, cartridge) but was longer and heavier. The .303" version of the Vickers proved almost as effective against the light, unarmoured aircraft structures of the time, and it was much lighter as well as faster-firing, so the RAF decided not to proceed with a heavy machine gun. By the mid-1930s, when the increasing performance and toughness of aircraft began to cast doubt on the future of rifle-calibre guns, the RAF opted for the greater destructive power of a 20mm cannon, choosing the French Hispano HS 404. A few American .5" Browning M2 guns were used late in the Second World War but apart from this no heavy machine guns were used by the RAF.
The Vickers wasn't the only .5" gun considered by the RAF. BSA (Birmingham Small Arms) offered their Model 1924 gun for aircraft observers. It was intended to be flexibly mounted so used a long-recoil mechanism to soften the recoil kick, and was fed by a pan magazine on top of the gun. Initially, this used BSA's own ammunition but it was later slightly modified to use the Vickers cartridge. The RAF rejected it as being too heavy, too slow-firing (only about 400 rpm) and having too small an ammunition capacity (37 rounds).
Vickers may not have had much success in selling their big gun to the RAF but it attracted foreign interest. The British Government didn't like Vickers selling their latest equipment abroad so Vickers slightly modified the cartridge case to make it semi-rimmed 12.7x80SR) and sold it to the Italians. They used it in their own Breda-SAFAT and Scotti aircraft guns and also passed it on to the Japanese Army, who developed an aircraft gun based on a smaller version of the Browning M2, known as the Ho-103, to use the cartridge. Vickers knew the cartridge as the V.565 as their standard bullet for it weighed 565 grains (36.5 grams) but various different loadings, including HE, were developed by the Italians and Japanese.
The Naval Guns
The naval version of the Vickers .5" was the most successful. It was initially offered in a curious four-barrel mounting in which the guns were stacked vertically, which in 1939 was the RN's standard short-range AA equipment. This was manually-operated, but later in the war a power-operated twin mounting (with side-by-side guns) was used in motor gun boats and similar craft. As an AA gun it soon proved insufficiently powerful and was gradually replaced by the 20mm Oerlikon.
The Army Guns
The British Army only used its .5" Vickers in AFV mountings. The Infantry Tank Mk 1 was equipped with one of these guns in a one-man turret, but apart from this the .5" was usually paired with a .303" Vickers in armoured cars and light tanks.
Early in the Second World War both Vickers .303" and .5" guns were replaced in their AFV roles by two guns from Czechoslovakia, the 7.9mm ZB vz/53 and 15mm ZB vz/60. These were both known as "BESAs" in British service.
The Class D
Much less well known is the Vickers .5" Class D or HV (for high velocity), also developed in the mid-1920s. This was basically a lengthened version of the usual .5" gun, designed around a much bigger and more powerful 12.7x120SR cartridge, known as the V.664 or V.690 (with 43 or 45 gram bullets; the latter became standard). The barrel was water-cooled as usual and rate of fire was 350-450 rpm. This was offered primarily as an AA gun, in single or twin mountings, but was never fielded by Britain. It seems that ammunition was supplied to both Japan and China, so presumably some guns were sold to these countries, but no details have emerged.
Rather less information has survived about three other Vickers projects; the 1" gun, the 13.2mm Vickers-Berthier and the .661" naval AA gun.
The 1" (25.4mm) gun was developed before the First World War, apparently for both aircraft and ground use. It was made under licence by Terni in Italy, who in the early 1920s sold some to the Swedish navy for installation as AA guns in four of their submarines.
Nothing is known about the 13.2mm Vickers-Berthier, except that the Berthier mechanism was designed by a Frenchman and also used in the .303" Vickers K or GO (gas-operated) aircraft gun. It is presumed that the gun was designed around the usual 13.2x99 Hotchkiss cartridge which was manufactured in the UK. No use for the gun is known.
Finally, the big .661" Vickers naval AA gun. This was designed in the mid-1930s as a replacement for the .5" gun, but development was stopped when it was decided to buy the 20mm Oerlikon instead. Little is known about the gun (no illustrations seem to have survived), but some examples of the massive 16.8x149SR cartridge do exist.
FOR PICTURES OF THE GUNS AND AMMUNITION, PLEASE SEE THE VERSION OF THIS ARTICLE ON MY WEBSITE: http://www.users.globalnet.co.uk/~autogun/
Thanks are due to the Curator and Staff of the Ministry of Defence Pattern Room, which supplied the black and white photos used to illustrate this article.
More information about the Vickers, Breda-SAFAT, Scotti, Ho-103 and BESA guns and ammunition mentioned in this article are included in the author's book: "Rapid Fire - The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces." Details on the military gun and ammunition website, address above.
For further information about the development of the Vickers cartridges, see: Labbett, P. British Small Arms Ammunition 1864-1938. Privately published (UK, 1993)