THE .5" VICKERS GUNS AND AMMUNITION

O Anthony G Williams

Amended 7 November 2005

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 inch or 11.5 mm) but in British service was overwhelmingly used in ,303 inch (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 37 mm or 40 mm. The first of these was the Maxim one-pounder (1 pdr) 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 heavier versions. The first of the these was the 1 % pdr (37xl23R) just before the First World War (this was experimentally fitted to the R-31 airship, in a circular top mounting), but shortly afterwards this was replaced by the 2 pdr (4Ox158R) 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 inch machine guns, which are much less well known. This account is intended to describe the various experimental and service weapons and their ammunition, developed mainly in the interwar period, some of which saw service but several of which did not.

Ammunition Development

The origin of the .5 inch 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 11 mm 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, which required a better armour-piercing performance than rifle-calibre guns could achieve.

Although the German 13 mm Mauser MI918 anti-tank rifle and the associated TuF (Tank und Flieger, after the intended targets) heavy machine gun are now famous, the parallel British developments are not. These were based around a .600/.500 inch 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 has survived) 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 12.7~81 case and was known by Vickers as the .5V/580, after the bullet weight in grains (37.5 grams). Muzzle velocity was around 750 rnls and total cartridge weight 83 g. The ammunition was officially adopted for service in 1924.

Several different loadings of the .5V/580 round were developed for British service, as follows:

. Ball Mark 1.2: 580 grain bullet with two-piece core (front aluminium, rear lead). Approved for service 1924, but not issued. . Ball Mark 1l.z: 580 grain bullet as above, muzzle velocity 2,540 fps (774 rnls). Approved for service 1925. . Ball Mark II (cordite propellant): approved for land service 1933. . Armour Piercing W. Mark I .z: bullet with hardened steel core and lead sleeve and tip filler. Approved for service 1925. To pass proof, seven out of ten bullets had to penetrate 18 mm of armour plate at 100 yards range at 0 (90) degrees, and 70% also had to penetrate 14 mm armour striking at 20 (70) degrees. . Armour Piercing W. Mark 1 (cordite propellant): as above, approved for land service 1933. . Semi Armour Piercing F Mark 1 .z: bullet as AP except steel core not hardened. 2,470 fps (753 rnls). Approved for naval use 1938. To pass proof, 70% of bullets had to penetrate 15 mm armour plate at 100 yards and 0 (90) degrees. . SAP Tracer FG Mark 1 .z, ll.z, 1ll.z: bullets weighed 542, 549 and 515 grains respectively (35.1, 35.6, 33.4 g), all at 2,470 fps (753 rnls). They all had a steel core with a tracer cavity drilled in the base, and all traced to 800 yards (730 m); the Mks l l and Ill had a dark trace (i.e. tracer did not illuminate until 100 yards from muzzle). All were approved between 1940 and 1944. All had to achieve the same penetration

WEB.001.0002 figure as the SAP F Mk I .z. . Incendiary B Mark 1.z: bullet weighed 562 grains (36.4 g) and was similar in design to the ,303 inch B Mk. VII (i.e., a simplified "De Wilde"). Within the jacket was a steel sleeve containing 28 grains of incendiary composition with a further 2 grains of QF composition held in the jacket tip. Introduced after 1939.

A photo of two sectioned cartridges - FG Mk I z SAP (left) and Mk B l z incendiary - is shown below (Courtesy of 'PzGr40')

and considerably cheaper.

All of the bullets in British service were flat-based which limited their maximum ballistic range to 4,265 yards (3,900 m). They could achieve a maximum altitude of 9,500 feet (2,900 m). Of course, the effective ranges were very much less than this; they were probably in the region of 820 yards (750 m) against aircrafl and 1,640 yards (1,500 m) against small surface targets. Tests carried out in 1928 showed the gun elevations (in minutes of angle) required to strike a target at the following ranges (in yards):

1 600 RANGE 1 200 1 300 1 500 1 800 1 1000 1 1200 1 1500 1 1700 1 2000 ELEVATION^ 4 1 5 1 13 1 17 1 29.5 1 44 1 59.25 1 88 1117 .25 1 165.25

The elevation of 165.25 minutes required to achieve 2,000 yards (1,830 m) equals 2.75 degrees.

The British Guns and the Browning Tests

The new Vickers .5 inch 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 by the removal of the delay pawl which held the crank until the barrel returned to battery -stronger buffer springs were also fitted. The air-force version combined the 700 rpm rate of fire with an air-cooled barrel. The army and naval versions had the traditional large-diameter fluted water-cooling jacket, just like the rifle-calibre version, but the aircrafl gun looked radically different, with flat, tapered plates running each side of the barrel. The weight of the aircrafl gun was 53 lbs (24 kg), the others weighed 57 lbs (26 kg) (without cooling water, which added 10 lbs - 4.5 kg). Barrel lengths were 31 inches (79 cm) or 62 calibres, overall lengths 47-53 inches (1 19-136 cm). The gun barrel recoiled a maximum of 1.25 inches (31.75 mm) and a recoil pull of 385 lbs (175 kg) was developed. The guns were belt-fed, using either a web belt (initially) or a disintegrating steel link type, with 100 rounds in the belt - a loaded belt weighed 24 lbs (10.9 kg).

During the 1920s the British tested an early .5 inch Vickers in comparison with the M I 924 version of the .5 inch Browning gun (the improved M2 was not introduced until the early 1930s). The Browning was designed around a longer and more powerful cartridge (1 2 .7~99 instead of 12.7~81) which typically fired bullets weighing 71 0 grains (46 g) at 2,900 fps (880 mls), generating around two-thirds more muzzle energy. A report, dated 1928, of the tests by the Admiralty of the water-cooled versions of the guns has survived. This reveals the following:

Data Weight of gun (no water) Quantity of water Weight of 100 rounds in web belt Weight of 100 rounds in links Weight of web belt Weight of 100 links Length of gun

Performance comparison:

Time taken to shift lock Time taken to fill 100 rounds we belt Time taken to fill 100 rounds link belt Rate of fire

Mechanisms: Vickers rated superior, as consists of only two parts (lock and feed box) compared with three (bolt, feed box and recoil buffer). The Vickers lock takes only one-third the time to replace, the feed box is also quicker to replace as well as being more reliable, and the feed being driven by gun recoil has no ill effect on the operation of the lock.

Time taken to shift belt I 16 seconds I 10 seconds

0.5 inch Vickers 54 lb (25 kg)

3.5 quarts (4.0 litres) = 10 lbs (4.5 kg) 20 lb (9.1 kg)

23 lbs 8 oz (10.7 kg) 2 lbs 5 oz (1.05 kg) 5 lbs 12 oz (2.6 kg)

4 feet exc flash excluder (122 cm)

Rate of Fire: both can be adjusted up to 750 rpm, but the Vickers can be adjusted by means of a crank check lever which can be regulated during firing, while the Browning requires the back plate to be removed to adjust the recoil buffer.

0.5 inch Browning 66.5 lb (30 kg)

6 quarts (6.8 litres) = 17 lbs (7.7 kg) 27 lb 2 oz (12.3 kg)

30 lbs 11 oz (13.9 kg) 7 oz (0.2 kg) 4 lb (1.8 kg)

4 feet 7 inches ( I 40 cm)

Ammunition feed operated by I Recoil of gun I Recoil of bolt

15 seconds 4 minutes 30 seconds 4 minutes 30 seconds

400 to 750 rpm

Temperature: the much larger water capacity of the Browning kept the barrel cooler, as shown below:

50 seconds 5 minutes 45 seconds 3 minutes 20 seconds

500 to 750 rpm

. . - - . . . . . . . . .

TEMPERAT-RES h DEGREES F C

Immediately after 400 rounds rapid:

- at muzzle - half-way down barrel -a t chamber

Choking of Barrel (i.e. fouling by bullet jacket deposits): slightly greater in the Vickers due partly to higher barrel temperatures and partly to a difference in hardness in the bullet casing (jacket). It was noted that this was less with AP bullets

Immediately after 600 rounds at 60 rpm:

- at muzzle - half-way down barrel

Fouling and grit: both guns performed satisfactorily, but it was noted that the Browning ended up with more grit in the mechanism due to it being more exposed by the opening of the gun casing. Also, after prolonged gun firing the Browning's mechanism was coated with black fouling while the Vickers' was clean.

V cders

I

Control: in both guns, the vibration was too severe to keep them on target so shoulder stocks were recommended for accuracy.

Bro>,n ng

500 (260) 250 (1 20) 150 (65)

-a t chamber I 250 (120) I 150 (65)

I

Belts and filling machines: neither web belt was found to be satisfactory. The Vickers belt was made using metal spacing strips and eyelets, which were inadequately secured, while the Browning's was stitched and could only be used two or three times. Both metal link belts were satisfactory. The Browning had filling machines for both types of belt (the metal belt filler was commended, the web one condemned), the Vickers had none.

31 0 (1 55) 150 (65) 50 (1 0)

400 (205)

Reliability: it was noted that the Vickers was an early example and suffered some problems, but these were corrected with modified parts during the trials and it was then very reliable. The Browning was reliable at high rates of fire but less so at lower RoFs, especially at higher elevations. Any kink in the belt would cause a failure to feed. The Browning's casing fractured during the test.

300 (1 50)

Conclusion (reproduced in full):

"The results of the trials lead to the conclusion that the .5-inch Vickers has the following advantages:

370 (1 90)

a. Greater reliability b. Wear and failure of parts - if any - are to minor parts that can be readily replaced. C. Care and maintenance is easier to the inexpert, on account of its less complicated recoil and buffer

mechanisms. d. The mechanism and functioning of the gun requires less special or expert knowledge to obtain a good,

reliable performance, and is more readily understood by the average seaman, who already receives training in the similar mechanism of the ,303-inch gun.

e. Readily converted to right or lefl gun. f. From a general technical point of view, it is the opinion that the fundamental principle of the mechanism

and the action of the Vickers gun is superior to that of the Browning, and is more certain in its action generally.

250 (1 20)

The .5-inch Vickers gun is therefore recommended for the Naval service in preference to the Browning gun."

The Aircraft Guns

The RAF also evaluated the .5 inch Vickers and Browning guns. The results were inconclusive; the Browning was more powerful but was longer and heavier. It was concluded that the ,303 inch version of the Vickers was almost as effective as the HMGs against the light, unarmoured aircrafl structures of the time and it was much lighter as well as faster-firing. The RAF accordingly decided not to proceed with a heavy machine gun, while noting that any widespread adoption of armour for military aircraft would force a re-think. By the mid-l930s, when the increasing performance and toughness of aircrafl began to cast doubt on the future of rifle-calibre guns, the RAF opted for the greater destructive power of a 20 mm cannon, choosing the French Hispano HS 404. A few American .5 inch Browning M2 guns were used late in the Second World War in applications for which the Hispano would have been too big and heavy, but apart from this no heavy machine guns were used

WEB.001.0012 up version, the 1 pdr Mark Ill in 37x69R calibre, which saw brief service with the RFC as an aircrafl gun in W 1 (it is sometimes confused with the much larger 1 pdr "Pom pom"). The improved Mk V version reportedly saw experimental use postwar in airships. Two views of different versions of the Vickers 1 inch are shown below.

The 1 inch Vickers should not be confused with the 25.4mm Vickers which was a mid-1930s naval AA gun. Details of the gun and its ammunition are available HERE. The photo shows three rare Vickers cartridges for comparison: the .50 HV, the 1 inch (25x87R) and the 25.4mm (25x189).

http://www.vickersmachinegun.org.uk~

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