Info: RAF Guns of WW II

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Info: RAF Guns of WW II

Postby Robert Hurst » 24 Feb 2003 12:47

Hi

The 7.7 mm (0.303 in) Vickers Gas-Operated Mk1 No.1

This gun had several official and unofficial titles. Its official service title was is shown above, Vickers called it the Class K; but in the RAF and FAA it was usually referred to as the VGO.

In the mid-thirties, gunners in the open cockpits of RAF and FAA multi-seat aircraft were still armed with the Lewis gun, but it was becoming obvious that this would have to be replaced with a more up-to-date design. Trials had just been carried out for a fixed gun, which resulted in the selection of the Colt Browning, but it was decided that a second gun was needed for the free position of bomber aircraft, and also to provide a 'second string'. At Martlesham Heath in September 1935 six types of gun were submitted for what could have been highly lucrative production contracts. The final choice was narrowed down to between the French Darne and the Vickers Class K. The French Darne was a belt-fed, gas-operated gun which, because of its short bolt stroke had a cyclic rate of 1,700 rpm. The vickers was a sturdy drum-fed gun, ideal for pivoted mountings, and because it was a simpler design, it was easier to service. Owing to the disagreement among the evaluation experts, Air Vice Marshal Dowding decided to conduct air firing tests personally, and Vickers emerged the winner. The Crayford works were given an initial order for 3,000 guns, and the first 200 were delivered in 1937.

Design History and operation

Foreseeing the need for a light machine gun for infantry, Vickers had acquiired the rights to a design by the French lieutenant Andre Berthier in 1918. However, by 1934 the British Army selected the Bren gun instead, which was based on a Czech design. The Vickers weapon had been found light and easily manouevrable, but it was prone to component failure and had a rather slow rate of fire. Vickers decided to redesign it, and a team led by Percy Higson produced a better weapon with a cyclic rate of 1,050 rpm. As the Class K, it was then ready for the 1935 RAF trials, and was given a very favourable report by the two principal armament experts at Martlesham Heath, Major H.S.V. Thompson and Captain E.S.R. Adams.

The gun was cocked by pulling back a handle on the left side. The breech-block was retained at the rear of the receiver on a projection at the back of the piston rod. When the trigger was pressed, the rod was driven forward by the force of the main spring, carrying with it the breech-block, which pushed a cartridge from the magazine into the chamber. As the piston continued to move forward, the rear of the breech-block was engaged on a sloping projection on the rear of the piston, and was forced in front of a locking shoulder on the main body. The floating firing pin was then struck by a projection on the rear of the rod, firing the cartridge. The gas pressure impinged on the head of the piston housed beneath the barrel, driving it to the rear, compressing the main spring and unlocking and withdrawing the breech-block. The rearward movement of the block extracted the case and ejected it into a container at the side of the gun. A saftey catch was incorporated into the hand grip which rendered the gun safe when not in use. After final assembly at Crayford, the guns were proof-fired with ammunition containing 25 per cent more charge than normal. They were then tested for automatic fire, first in a horizontal position, then at an angle of 90 degrees.

The pistons in the early production guns tended to fail after firing 1,000 rounds or so, Higson was able to correct this and other small faults. The modified gun proved to be highly efficient, the minimum life of any component being 10,000 rounds - a great improvement over the Lewis gun, for which replacement parts had to be carried in the aircraft. The 47-round magazine was dropped in favour of a 100-round drum, which gave a more realistic ammunition supply. Higson stressed the modest recoil, the absence of external moving parts, and the fact that the gun could be dismantled in a few seconds with no other tools than an empty cartridge case and a pen-knife.

Initially, armourers had trouble tensioning the spring of the 100-round magazine, but limiting the load to 97 rounds overcame the problem. Stoppages did occur, the most frequent cause being defective ammunition and badly filled magazines. Lack of maintenance could lead to short or broken firing pins, defective extractors and broken springs. Perhaps the most disturbing experience was not a gun which stopped firing, but a gun which would not stop!

The gun proved so successful that a cable-operated version was specified for all turrets mounting a single gun and (in the case of Blenheims and Beauforts) twin guns. Vickers produced a belt fed fixed version, for which ammunition was supplied from 300 or 600 round tanks. Some early Blenheim 1 aircraft had the fixed version of this gun, but almost all were used on pivoted mountings and turrets. The Bristol Bombay nose and tail turrets each had a single gun, as did the front turrets of the Whitley, Sunderland and Lerwick flying-boats. When the gun was fired from these turrets the piston rods often broke. It was eventually found that the part of the gas cylinder outside the turret was chilled by the slipstream, whereas the section inside the turret soon reached a high temperature after a few bursts were fired, causing the piston to seize. The cylinder diameter was increased but, although this reduced the failure rate, gunners of No.5 Group (Wellingtons) were advised to carry spares for the side hatch guns. Being self-contained and needing no belt boxes, the gun was used in the nose position of all later Halifax bombers, and Sunderland and Beauforts used it as additional armament to power turrets. Pivoted guns were usually sighted by 51 mm (2 in) ring-and-bead sights, but Mk 111 reflector sites were also used on both free-mounted and turret installations.

Many army units used the VGO. The Long Range Desert Group of the 8th Army, as well as the SAS, found that it was far less liable to stoppages than the Bren, and it was also used by the Indian Army (Vickers Berthier or VB Mks 1, 2, 3 & 3B) instead of the Bren.

Details of the 7.7 mm (0.303 in) Vickers Gas-Operated

Calibre: 7.7 mm (0.303 in)
Weight: 9.5 kg (20.5 lb)
Muzzle Velocity: 732 m/sec (2,400 ft/sec)
Cyclic Rate: 950-1,100 rpm
Maximum Range: 914 m (1,000 yds)
Weight of Bullet (Mk VIII): 11.34 grams (0.4 oz)
Action: Gas-operated
Ammunition Feed: 47-(later 97-) round drum
Cooling: Air
Length: 1,016 mm (40 in)
Rifling: Five grooves, left hand.

The above text and photos were taken from "British Aircraft Armament Vol 2: RAF Guns and Gunsights", by R. Wallace Clark.

If anyone would like to comment about anything in this section, please feel free to do so.

Regards

Bob
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Postby Robert Hurst » 24 Feb 2003 16:17

Hi

7.7 mm (0.303 in) Browning - Pt 1

In 1933, at the request of the US Army Air Corps, two 7.62 mm (0.300 in) versions of the 12.7 mm (0.50 in )M2 were produced. The first was a pilot's gun, while the second, the M9/402, was designed as a pivoted observer's gun with a higher rate of fire and longer barrel length. Just after these guns had been produced, the RAF decided to hold competitive trials to select a modern automatic gun. The guns tested were the Vickers, Hotchkiss, Darne, Madsen and the Colt MG40 and MG40/2. The winner was the Colt 40/2, which proved the to have the best all round performance.

Once the gun had been selected, the Martlesham Heath gun section under Major Adams conducted Service trials. It was found that the cordite-filled 7.7 mm (0.303 in) cartridges used in Britain caused serious trouble (most countries used nitrocellulose propellent, which was less sensitive to heat than cordite). When a long burst was fired a round remained in the chamber, and the cordite then detonated. Major Adams redesigned the action to hold the breech-block to the rear with the chamber empty. The first trials of production guns from BSA showed a weakness in the feed. This meant a further extensive redesign, until the final gun was quite different from the MG40/2.

The Browning gun was the first in RAF use to have the facility of adjusting the barrel in relation to the breech-block. Some armourers adjusted the barrel too far forward, leaving too much of the case protruding from the barrel, so that the end of the round was blown off causing a 'separated case' stoppage. With experience this problem was overcome, and durng the Battle of Britain, if a fighter returned from a sortie with a separated case stoppage the armourer responsible was put on a charge. Trouble was also caused by excessive fouling of the muzzle attachment, the guns seizing after about 200 rounds. A sharp pen-knife seemed the best way to clear the hard residue. In 1940 BSA redesigned the muzzle attachment by adding cooling fins and chromium-plating the bore of the unit. This modification caused a hold-up to production at a vital period, but the gun could then fire 300 and more rounds without fouling. After the troubles were rectified, production at BSA, Vicker-Armstrongs and sub-contractors kept up with the demands of the Service (one Hurricane and Stirling needed 16 guns).

The text and photos were taken from "British Aircraft Armament Vol. 2: RAF Guns and Gunsights), by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 24 Feb 2003 16:39

Hi

7.7 mm (0.303 in) Browning - Pt 2

The Browning was a recoil-operated gun with safety features which ensured near trouble-free operation. The gun was fired when the rear sear was depressed. This was done by hand, or by pneumatic, hydraulic or electrical solenoid actuation, depending on the installation. With sufficient maintenance, malfunctions were minimal. The most usual stoppage was caused by rogue ammuntion or badly made-up belts, though the links would also sometimes jam in the ejection outlet. Turret gunners could clear stoppages with a hooked tool kept handy in the turret, and gunners also kept a looped wire or hooked metal cocking tool to clear the gun. Stoppages were reduced after special belt-making machines were introduced.

Very cold conditions could also lead to problems. Heaters were provided in fighter gun bays, but oil spillage in some power turrets made heaters a safety hazard. Anti-freeze oil helped, and one Bomber Group fixed a paper seal over the cartridge ejection slot to stop the fierce draught which could enter the aperture. The 'fire and safe' unit mounted on the side of the gun body was operated by a pneumatic actuator on the same pressure line as the sear release unit on fighter aircraft. Turret guns were fired by hydraulic units or electrical solenoids controlled by triggers or push buttons on the turret control handle. The guns were made safe by pressing a release pin at the back of the fire and safe unit.

Each gun was marked with its number and Mark designation. Marks 1 and 11 were almost identical, having the early muzzle attachment; Mk11* guns were fitted with the BSA modified unit.

The Browning was rarely used as a free-mounted gun, except in Beaufighter TF Mk.Xs of Coastal Command, where the observer's cupola was so small that the ammunition drums of a Vickers could not be accommodated. Otherwise, when a free-mounted gun was needed, the Vickers K was used.

Browning Gun Production

A total of 460,000 complete Brownings were manufactured in the UK with spares for another 100,000. Most of these were manufactured by BSA but an extensive sub-contract scheme was set up in 1941, BSA supplying key personnel and supervising the work. Series production started in 1938, when 3,809 were produced, and production figures rose until in 1942 16, 300 were completed. Production contracts were competed by the end of 1944, and in 1945 the lines were closed down.

Details of the 7.7 mm (0.303 in) Browning

Calibre: 7.7 mm (0.303 in)
Action: Recoil
Cyclic rate: 1,150 rpm
Weight: 9.9 kg (21 lb 14 oz)
Muzzle velocity: 811 m /sec (2,660 ft/sec)
Ammunition feed: Metal links
Cooling: Air
Rifling: Five grooves, left-hand twist, 1 turn/10 calibres
Length: 1,130 mm (3ft 8 in)
Weight of Bullet (Mk VIII): 11.34 grams (0.4 oz)
Maximum Range: 914 m (3,000 yds)

The above text and photos were taken from "British Aircraft Armament Vol 2: Guns and Gunsights", by R Wallace Clarke.
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Postby Robert Hurst » 25 Feb 2003 16:09

Hi

Browning Ammunition Belts

Browning ammuntion belts were made up in the early war years by armourers using hand-wound belt-making machines. On some occasions the bullets were even inserted into the links by hand. The make-up of the belts varied with the unit: in most Bomber Command Groups one in five rounds was tracer, but AP and incendiary rounds were often included, especially in fighter units. When the Plessey electrically powered belt-making machine was introduced, the work of the armourer became a little less irksome. The bullets were fed into a hopper one end, and when the machine was switched on a continuous belt was produced from the other.

Identification of 7.7 mm (0.303 in) ammunition used in the Browning and Vickers K.

Service ammunition is identified in several ways, viz:

1. Labels on the container; 2. A code stamped on the base of the cartridge case; 3. Coloured dye on the annulus of the round (centre of the base); and 4. Colouring of the bullet tip (1939-1945)

The base marking gives the main details. These consist of: A. Code initials of manufacturer; B. Year of manufacture; C. Type of propellent (usually only Z for nitrocellulose); D. Mark of cartridge; and E. Type of bullet. The annulus colour code is found in the centre of the base, and signifies the following: Black: Ball until 1918; Purple: Ball after 1918; Blue: Incendiary: Orange: Explosive, including PSA; Red: Tracer.

During the 1939-45 war, station armourers needed a more instant way of identifying special ammunition. The method adopted was to colour the tips of the bullets, the code being as follows: Blue tip: some marks of incendiary; White tip: air-to-air short-range day tracer; Grey tip: air-to-air short-range night tracer; Black tip: observation bullet; No colour: ball.

Head Stamps

Each manufacturer was given a code to be used on the head stamp on the base of the round. The main makers were: BE - ROF Blackpole (1939-45), CP - Crompton Parkinson, E - Eley, FN - Fabrique Nationale, K - Kynock (ICI) - at various factories (K2, K3, K4 & K5), RG - ROF Radway Green, RL and RG - Royal Laboratory Woolich, RW - Rudge Whitworth, SR - ROF Spennymore. Bullet types were also shown on the head stamps, as: AA - PSA or Pomeroy, B - Buckingham explosive, F - semi-armour piercing, G -SPG tracer, K - Brock incendiary, R - Explosive from 1918, T or G - Tracer, W - armour-piercing, Z - Nitrocellulose propellent after 1917. Ball ammunition was stamped VII with no letter.

The above text and photos were taken from " British Aircraft Armament Vol.2: RAF Guns and Gunsights", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 25 Feb 2003 16:32

Hi

12.7 mm (0.50 in) Browning

As the war progressed, the RAF received many US warplanes, and the 'fifty caliber' Browning's fire power was appreciated by British aircrews.

Various UK manufacturers produced turrets armed with the gun in the last years of the war. The Spitfire F.Mk.IXE was also equipped with these weapons, and other British fighters were fitted with them experimentally.

Action

The gun can initially be charged manually or, in turret guns, by hydraulic or pneumatic units. Turret guns are fired by relay-controlled solenoids, free guns by twin triggers at the rear in an E II cradle unit.

When the gun is fired, recoil carries the barrel, barrel extension and bolt backwards a short distance. This unlocks the bolt from the barrel extension and the bolt is thrown further to the rear against the main spring. The empty case is withdrawn by the bolt and the next round extracted from the belt. As the bolt travels forward, the case is ejected and the next round moves into the breech. The rearward motion of the barrel and extension is checked by the oil buffer and spring, which then drives them forward again. This locks the bolt to the firing pin to fire the new round. This cycle continues as long as the sear is depressed and
ammunition is available.

The rimless ammunition is unusual in that there is no copper driving band normally found on such weapons: in consequence, the armour-piercing rounds caused heavy barrel wear.

12.7 mm Browning Cartridge Identification

Ball: Gilded metal (copper-coloured)
Armour-Piercing: Black tip
Tracer: Red tip
Incendiary: Light blue tip
Dummy: Hole in case

Details of 12.7 mm (0.50 in) Browning

Calibre: 12.7 mm (0.50 in)
Action: Recoil
Cyclic rate:
(M2): 750/850 rpm
(M3): 1,200 rpm
Weight: 29 kg (64 lb)
Muzzle velocity: 838 m/sec (2,750 ft/sec)
Cooling: Air
Rifling: Eight grooves, right hand
Length: 1.42 m (4ft 8 in)
Weight of Bullet: 39.69 grams (1.4 oz)
Maximum Range: 6,583 m (7,200 yds)

Rolls-Royce 12.7 mm (0.50 in) Experimental Gun

The Rolls-Royce Design Department designed two heavy machine guns which had several new features. The first design was gas-operated, with a cyclic rate of 650 rpm, the other was to be recoil-operated. It was decided to concentrate on a recoil-operated weapon. Viale constructed the body and breech cover of RR50 aluminium alloy. The barrel was shorter than the Browning and this, combined with the alloy construction, reduced the weight. The gun fired from a locked breech. As the breech-block recoiled, a pair of accelerators carried back a wedge-shaped balance-piece and retracted the striker pin.

The gun was tested at the Proof and Experimental Establishment at Pendine Sands in March 1941. It was found that the short barrel caused an abnormally large flash, and a long flash eliminator was added. The trials revealed minor snags, and Rolls-Royce decided to redesign the gun for 0.55 in Boys anti-tank ammunition. This development was showing great promise when the company decided to cancel all armament work.

Details of the Rolls-Royce 12.7 mm (0.50 in) experimental gun.

Calibre: 12.7 mm (0.50 in)
Action: Recoil
Cyclic rate: 1,000 rpm
Weight: 22.2 kg (49 lb)
Muzzle velocity: 713 m/sec (2,340 ft/sec)
Ammunition feed: Disintegrating belt
Cooling: Air
Rifling: Four grooves, right-hand twist
length: 1,270 mm (50 in)

The text and photos were taken from "British Aircraft Armament Vol2: RAF Guns and Gunsights", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 26 Feb 2003 16:30

Hi

20 mm Hispano Suiza Cannon - Pt 1

In 1930 the Swiss Oerlikon company designed a 20 mm (0.78 in) cannon to be mounted between the cylinder banks of geared vee type aero-engines, the engine absorbing the recoil forces. The gun fired through the propeller shaft as in the Hispano-Suiza WW1 mounting. In 1932 Hispano-Suiza purchased some Oerlikon guns for use in conjunction with their HS.12x aero-engine, but in spite of much development work the project was abandoned owing to problems with the gun. The company then decided to design a new 20 mm gun based on the action of the German Becker cannon of 1918, and after early design faults were sorted out the new gun, designated the Hispano-Suiza Type 404 'Moteur Canon', proved to be an outstanding success. A production contract was received from the French Government, and the first aircraft to be fitted was the new low-wing D.510 fighter, one Hispano being mounted in each wing outboard of the propeller disc. The performance of the gun was so good that the air arms of all major powers evaluated examples for possible licensed production. In 1935 the British Air Staff decided that sooner or later a heavy-calibre gun would have to be introduced to counter the introduction of armour in future aircraft. The Air Ministry Gun Section advised the adoption of the Hispano 'Moteur Canon' as no British design was available. Members of the Air Staff, accompanied by the Head of the Air Ministry gun section, Major H.S.V. Thompson, visited the Hispano works in Paris, and after a demonstration of the gun, convinced all present that the Hispano should be adopted by the RAF, and an order was placed for six guns. The Section had conducted a series of tests on a special gun during the previous year, and several features, including the positive locking of the breech when the round was fired, had convinced them that the weapon was superior to other weapons with blowback actions.

Briefly, the action sequences was as follows: As the breech-block was released by the sear it travelled forward, feeding a round into the chamber. The breech was then locked and the round fired. Diverted gas pressure then acted on the piston, mounted over the barrel; this unlocked the breech, and gas thrust on the case forced the breech-block to the rear, the empty case being extracted from the chamber and ejected. A pneumatic recocking unit, operated from the aircraft's system, was built into the gun body. The gun was fitted with a recoil reducer and a heavy spring, damped front mounting unit. The firing sear was released by Bowden cable, pneumatic- or solenoid-operated unit under the rear of the gun body.

The above text and photos were taken from " British Aircraft Armament Vol 2: Guns and Gunsights", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 27 Feb 2003 12:25

Hi

20 mm Hispano Suiza Cannon - Pt 2

When the decision was taken to accept the gun as a possible standard weapon for RAF fighters, the Air Staff realised that it would have to be manufactured in the UK. As the only gun-producing companies were fully committed to other weapons, it followed that new production facilities would have to be provided. After initial reservations, the Hispano-Suiza company finally agreed to form a British subsidiary company to manufacture the gun in England. A factory was built at Grantham which was to be known as The British Manufacturing and Research Company (BMARC for short). All dimensions were metric, and engineers from France helped to train the operatives. The first guns were proof-fired in January 1938. Several faults were found, some due to the inexperienced workforce, but others due to problems with the design which had not shown up on the hand-built guns tested in Paris. The return spring was prone to breakage, the extractor spring had a very short life, and the breech-locking system needed redesigning. Whilst these problems were being investigated at the Chatellerault works of Hispano-Suiza, Captain E.S.R.Adams, Senior Technical Officer of the Directorate of Armament Development, and experts from BSA investigated all aspects of the project. It was agreed that it would be very difficult to manufacture the gun at a normal engineering works if the need arose, and the Air Staff set up a team to produce British drawings and simplify the manufacturing process. Hispano-Suiza did not take kindly to this development, but after close co-operation between Captain Adams and Hispano engineers it was agreed to proceed.

Most of the defects had been sorted out by early 1940. Meanwhile, Mr John North at Boulton Paul had made other improvements to the design, and prepared the gun for turret mounting. The Air Staff had originally planned to introduce the gun for the new fighters which were to succeed the Spifire and Hurricane, but when the Munich crisis occurred the Air Staff suddenly directed that the new fighters coming off the production line should be fitted with the new gun. It was soon realised that the Grantham factory would not be able to produce the vastly increased number of guns required, and top priority was given for four new factories. A second, 'shadow ' factory was built at Grantham, another run by BSA, was constructed at Newcastle-under-Lyme, a new purpose-built factory was specially erected at Poole, and part of the Royal Small Arms Factory at Enfield-Lock was turned over to Hispano production. The first guns were delivered from these factories in early 1941, but the Grantham factory was able to provide several hundred guns for Spitfire Mk.1Bs in 1940. These aircraft took part in Service trials, and No.19 Sqn. took part in operations against German raiders with spectacular results, but the gun's debut was marred by faults in the ammunition feed, and was withdrawn from squadron use.

The above text and photos were taken from "British Aircraft Armament Vol 2: Guns and Gunsights", by R Wallace Clarke.

Regard

Bob
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Postby Robert Hurst » 28 Feb 2003 12:39

Hi

20 mm Hispano-Suiza Cannon Pt 3

Future development work was carried out at the BSA works, where the Air Ministry had set up a drawing office to produce the anglicised Hispano Mk II under the leadership of Captain Adams. The ammunition feed problem was mainly due to the use of a bulky 60-round drum, which could only be accommodated if the gun was mounted on its side. Just before the Germans overran the Hispano factory in Paris, Adams made a risky journey to the works and retrieved a newly designed belt-feed unit and a full set of working drawings. The production contract for the new feed units was given to the Molins Machine Company. This company progressively developed the feed unit until stoppages were brought down to an average of one very 1,500 rounds. The large 60-round magazines were still used on Beaufighter aircraft where the observer could change drums during operations. At last, RAF fighters were being armed with weapons second to none.

Most air forces opted for shell-firing guns in the 1930s because it was thought that explosive shells would destroy an aircraft with very few hits. This was not borne out by events; in fact trials often showed that solid ball ammuntion did as much damage as explosive rounds, which tended to explode directly on contact with armour or airframes without penetrating them. The heavy ball projectiles penetrated both, and was the main type of ammunition used in the early war years. However, it was then realised that an ideal round would first penetrate an airframe and then ignite the fuel or oil inside it. Incendiary ammuntion tended to break up, but a composite explosive/incendiary shell was found to be very effective. Known as HE/I, this new round was however less effective against armour. In July 1942 the semi-armour piercing incendiary (SAP/I) was introduced, with a tungsten nose and a shell containing an incendiary composition. On impact, the tip penetrated the armour, and there was then a flash of flame which ignited anything inflammable within 305 mm (12 in) of it. From mid-1942 these two types of ammuntion replaced other types, belts being made up equally of HE/I and SAP/I.

Tremendous skill and responsibility was required by squadron armourers. Considerable technical knowledge was essential, and very few stoppages were attributed to poor maintenance or servicing. Many modifications were introduced at squadron level. The recoil distance of the Hispano was critical for trouble-free firing. After one round was fired into the stop butts, the recoil distance had to be 20 mm (0.78 in) when cold. This proved to be very difficult to measure, until an armourer discovered that, if a piece of Plasticine was pressed on to the end of the piston so that it came into contact with the front face of the feed unit after firing, the recoil could be measured by using calipers on the resulting indentation.

Until the end of 1941, the British development of the Hispano was led by Captain Adams. It was then thought necessary to promote the younger generation of armament engineers, and the Hispano was passed over to Mr G.F.Wallace, who had co-ordinated the development of the belt-feed mechanism. The weapon was still not ideal for wing installations, the main problem being the length of the barrel. The gun had been designed to fit the Hispano engine, with the breech behind the engine and the barrel projecting through the propeller hub. The long barrel gave increased muzzle velocity, but when installed in fighter wings, some 610 mm (24 in) projected in front of the leading edge. Also, in late 1941 the cannon turret projects had been belatedly revived, and the need for a shorter gun was urgent.

As a first step towards achieving this, Wallace shortened a Mk II by 305 mm (12 in) and test-fired it at the Poole Ordnance Factory. Other than a slight reduction in muzzle velocity, performance was not affected. A small batch of Mk IIs with shortened barrels was supplied to Boulton Paul, Bristol and Parnall for use on experimental turrets. Wallace then made more fundamental modifications, increasing the cyclic rate and reducing the weight of the gun. Although the faster speed imposed more stress on the working parts, it was found that few guns fired as many as 1,000 rounds before the aircraft was lost in action, taken out of service or written off in an accident. Though the specification called for a service life of 10,000 rounds, it was agreed that this could safely be reduced to 2,000 in the interests of performance, the speed being increased from 650 to 750 rpm. Reductiojn in weight was achieved mainly by deleting the intregal cocking cylinder. This gave the pilot a means of recharging the gun in the air, but was rarely used - with three other guns, the pilot was often unaware of the stoppage.

After these modifications the gun was faster, lighter and shorter and in May 1943 a batch of modified guns, known as the Mk V, were tested at Boscombe Down. It was found that the front gun mounting would not stand up to the increased recoil forces. The US Army Air Force had adopted the Hispano for the P.38 and other aircraft, and had fitted a very efficient front mounting made by the Edgewater Co. An anglicised version was designed and produced which solved the recoil problem, and the Hispano Mk V was accepted for use on RAF aircraft for the next 30 years. During the last year of the war aircraft of the 2nd Tactical Air Force alone fired 13,500,000 rounds of 20 mm ammunition at a stoppage rate of one per 1,500 rounds fired, mostly due to badly made-up belts.

Details of the 20 mm Hispano Suiza

Calibre: 20 mm (0.78 in)
Action: Gas-operated
Cyclic Rate:
(Mk II):650 rpm
(Mk V): 750 rpm
Maximum Range: 9,144 m (10,000 yds)
Weight:
(Mk II): 49.4 kg (109 lb)
(Mk V): 38.1 kg (84 lb)
Length of Gun:
(Mk II): 2,514.6 mm (8ft 3.5 in)
(Mk V): 2,184.4 mm (7ft 2 in)
Muzzle Velocity:
(Mk II): 878 m/sec (2,880 ft/sec)
(Mk V): 838 m/sec (2,750 ft/sec)
Ammunition Feed:
(Mk II): 60-round drum/disintegrating links
(Mk V): Belt-feed (disintegrating links)
Cooling: Air
Rifling: Right Hand
Cocking:
(Mk II): Pneumatic Charger
(Mk V): By Ground Crew Only
Grooves: Nine at 7 degrees

Summary of Hispano-Suiza Aircraft Guns Made In The UK

Mk 1: First model, made to French drawings.
Mk II: Minor changes, made to British drawings.
Mk II*: Mk II with Mk III unlocking plates having no inertia blocks.
Mk III: Enfield designed, prototype only.
Mk IV: Mk II* with barrel shortened to 305 mm (12 in).
Mk V: Wallace modification: lighter, with special locking plates, short barrel, cyclic rate 750 rpm.
Mk 6(1): Modified to fit American cradle.
Mk 7: Electrically primed ammunition.
Mk 8*: Mk V modified to give 900 rpm.
Mk 9: Mk 8 with electrically primed ammunition:

Note:

1: Adoption of Arabic numbers

Projectile Identification

Ball: Black
Gun Functioning: White
Armour-Piercing: Black with white tip or white nose rings
Tracer: Black with stencilled red T in inverted circle
Semi-AP/High-Explosive/Incendiary: Red with red tip
Semi-AP/High-Explosive/Incendiary: Red lower body, buff upper body, white tip
High-Explosive: Buff
Incendiary: Red
High-Explosive/Incendiary: Green upper body, red lower body

Cartridge Headstamp Identification

BMARC: British Manufacturing and Research
GB: Greenwood and Batley
H: Halls Telephone Co. Ltd
K: ICI Birmingham (K3 and K2 indicate ICI Kynoch)
P&S: Plasters and Stampers
RC: Raleigh Cycle Co.
RG: Royal Ordnance Factory, Radway Green
RH: Raleigh Cycle Co.
ST: Royal Ordnance Factory, Steeton and Thorpe Arch
JES: Post-war drill/inspection

The above text photos were taken from"British Aircraft Armament Vol.2: Guns and Gunsights", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 28 Feb 2003 16:34

Hi

40 mm (1.57 in) Vickers S Gun - Pt 1

In 1936 the Air Staff decided to carry out a series of trials to find the minimum size of shell capable of destroying an aircraft with one hit. After various experiments it was found that any aircraft hit by a shell 40 mm (1.57 in) or over would probably not survive. So in 1938 a specification was issued for a 2 pdr gun suitable for aircraft. The obvious choice was Vickers-Armstrongs, but at a meeting at the Air Ministry E.W. (later Lord) Hives of Rolls-Royce announced that his company could produce such a weapon in 18 months, so both Rolls-Royce and Vickers-Armstrongs received development contracts.

The chief designer, at Crayford, Percy Higson, had foreseen the result of the projectile trials, and made sure by obtaining the conclusions long before they were officially announced. Thus by the end of 1938, only months after receiving the the order from the Air Ministry, Higson's gun was complete.

The gun used the long recoil system similar to the COW(1) gun. The new gun was smaller, had a much faster rate fo fire, and was fed by a magazine holding 15 of the big rounds. The gun fired the same 2 pdr shells as a much heavier naval gun also designed by Higson. In early 1939 Vickers submitted a scheme for mounting the gun in a large dorsal turret in a Wellington 'heavy fighter' with a predictor and a rangefinder. Such an aircraft it was claimed, could engage hostile formations at a range well beyond that of the fighters' defensive fire.

A prototype gun began testing in 1939, and suffered far fewer teething troubles than was usual with an entirely new gun. In early 1940 the gun was despatched to Woolich for Ordnance Board certification, where no faults occurred during extensive testing. A small production order soon followed for the gun, known at Vickers as the Class S. Vickers also went ahead at Brooklands with fitting the prototype Wellington Mk II (L4250) with the big mushroom-shaped 40 mm emplacement.

The company also submitted a fighter design to Specifcation F.22/39, mounting an S gun in the nose, the gunner having a sighting cupola similar to the turret. The S gun was also used in the Bristol B.16 nose turret installed in some Coastal Command Flying Fortress II aircraft for anti-submarine operations.

The text and photos were taken from "British Aiorcraft Armament Vol 2: Guns and Gunsights", by R Wallace Clarke

Regards

Bob
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Postby Robert Hurst » 01 Mar 2003 12:55

Hi

40 mm (1.57 in) Vickers S Gun - Pt 2

After the fall of France in June 1940 it was obvious that some means would have to be devised to knock out German tanks. Ordnance experts suggested that, if a suitable armour-piercing projectile could be devised, the S gun might provide one answer. A warhead was produced which would penetrate the German Panzers frontal armour, and an S gun was tested in a Beaufighter. Vickers were given an immediate order for 100 more guns, and Hawker Aircraft were asked to make the necessary structural alterations to a Hurricane to take the weight and recoil shock of an S gun under each wing. A mounting was devised by Higson, the big magazine proving difficult to accommodate. In the meantime a Mustang (AM106) was used to test the mounting and devise the best method of attack (the Mustang might have been a more suitable aircraft to use than the lower performance Hurricane).

The trials carried out from Boscombe Down proved very successful, and the first two production guns were fitted to a modified Hurricane. Known as the Mk IID, it was flown to Boscombe Down for assessment in September 1941. Attacks were conducted against a Valentine tank at the Lulworth range. The AP shells penetrated both the front and turret armour, and the go-ahead was given for a Mk IID squadron to be sent to North Africa. As the guns were virtually hand-made, it was decided to air-test every gun fitted to the Hurricanes. In the first test the empty cases of both guns failed to eject and jammed. Why this should have happened after prolonged firing tests remained a mystery, until someone realised that hitherto Vickers-made shells had been used. The Kynoch shells used in these tests had a slightly softer brass case, so that when fired they expanded fractionally more than the Vickers, and their rims were torn off by the extractor. As an interim measure, the rounds were slightly oiled (usually a punishable offence in the RAF, but accepted in this case as a stop-gap solution).

The officer in charge of the project was Wg Cdr. 'Dru' Drury, who was the driving force behind the Mk IID programme. He nearly crashed during early trials, when the two guns were first fired: the recoil caused the aircraft to dip nose down. He recovered just in time, but this remained a problem, and was countered by easing the nose up slightly at the moment of firing. The first squadron, No.6, began training at Shanar in Egypt on 20 April 1942, Drury taking charge of the first period of training. The gun was aimed by the usual Mk II reflector sight, but two Brownings loaded with tracer ammunition were retained and they gace a good indication of the impact point.

The first operation took place on 7 June, when two tanks and a number of trucks were destroyed. The squadron was in continuous action from this time. In early August two DFCs were awarded to No.6 Sqn pilots, F/Lt. Hillier pressing home an attack so low that his tailpane struck the tank he had hit. A captured German tank commander described how his company of 12 PzKpw IV tanks were attacked by No.6 Sqn. Six tanks were knocked out, the other six managed to escape, though one of these had its turret pierced right through. On the other hand No.6 Sqn suffered a high casualty rate: the guns slowed the aircraft by 64 km/h (40 mph), and even the fighter version was no match for the more agile and powerful Bf109F. With the appearance of rocket projectiles, the Hurricane was withdrawn from service in North Africa, although a few were used on what were virtually suicide attacks on V1 launching sites. Most were despatched to the Far East, where they were very effectively used by No.20 Sqn in Burma.

As the Vickers S gun was originally designed for air-to-air firing, the first shells used were HE. Although based on a naval ptojectile, the length of the round was increased to obtain the maximum explosive charge. In September 1941 Vickers designed the armour-piercing shell, known as the armour-piercing Mk I. Weighing 1.13 kg (2.5 lb), it was a solid projectile with a tungsten nose which could penetrate 50 mm (1.97 in) armour, and was the ammunition used in North Africa. Vickers-Armstrongs later produced a 3 lb shell for the gun which gave an increased penetration of 9 per cent. This was the final round, with the Service title AP Mark V. HE ammunition was used in Burma, where most targets were 'soft skinned'.

Details of the 40 mm Vickers S gun

Calibre: 40 mm (1.57 in)
Action: Recoil
Cyclic Rate: 125 rpm
Weight: 134 kg (295 lb)
Weight of Ammunition (HE):
(AP Mk 1): 1.134 kg (2 1/2 lb)
(AP Mk 5): 1.3608 (5 lb)
Armour Penetration (AP Mk 1): 50 mm (1.97 in)
(AP Mk V): 55 mm (2.17 in)
Muzzle Velocity: 549 m/sec (1,800 ft/sec)
Ammunition Feed: 15-round spring-loaded drum
Cooling: Air
Effective Range: 2,286 m (2,500 yds)

The above text and photos were taken from "Brirish Aircraft Armament Vol2; Guns and Gunsights", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 03 Mar 2003 12:19

Hi

40 mm Vickers S Gun - Pt 3

This section is for showing colour photos of the Hawker Hurricane Mk IID.

The photos were taken from "The Hamlyn Concise Guide to British Aircraft of World War II", by David Monday.

Regards

Bob
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Postby Robert Hurst » 03 Mar 2003 12:45

Hi

40 mm Rolls-Royce Gun

In September 1938, at a meeting called by the Air Staff to discus various aspects of aircraft armament manufacture and design, a member of the Air Staff asked how long it would take to produced a heavy-calibre aircraft gun. As related in the section dealing with the Vickers S gun, the General Manager of Rolls-Royce, Mr E.W.Hives, said that he could form a design team, and with engineering resources of his company, produce one in 18 months. The Air Staff decided to take him at his word and issued a development order for a 40 mm automatic gun. Accordingly, a gun design team was set up at the experimental works at Derby headed by Dr Mario Spirito Viale, a naturalised Italian who had previously been employed by Armstrong Siddeley Aircraft on engine design. The Air Ministry provided a 37 mm Coventry Ordnance Works gun of First World War vintage which it was thought could provide a design basis, but Viale had other ideas. He used the Degtyarev breech-locking system, modified to incorporate cams to force the locking struts apart. It was recoil-operated, the return of the barrel and breech-block being pneumatic. RR50 aluminium alloy was used for the gun cradle and parts of the recoil mechanism; this proved very succesful. Rounds were clipped four at a time onto an aluminium charger plate which could be replenished whilst the gun was being fired, but this rather basic system gave trouble and was replaced by an eight-round hopper in later versions.

Design work started in late 1938, and in February 1939 Viale was granted patents for some of the new features of the design. The prototype was completed in December of that year, and was despatched to Woolwich for proof firing, mounted on a Victorian gun carriage which, strange as it may seem, provided an ideal mounting, being both steady and transportable. The initial test was completed without mishap, and work proceeded on the magazine-feed system, which was to prove troublesome during test firing at Melton Mowbray in April 1940. During trials it was found that stoppages were in part due to the First World War design of the 40 mm (2-pdr) naval ammunition used, which was unable to withstand the high pressures involved. The gun was returned to Derby where further modificaton work was undertaken.

Whilst this was in progress the company was informed that operational experience had shown that damage caused by enemy 37 mm anti-aircraft guns had been far less than expected, and it had been decided to treat the project with less urgency. However, the Admiralty meanwhile had found that the defensive guns on their motor gunboats were completely inadequate, and the Rolls-Royce gun seemed a possible answer to this situation. So great was the need that the Navy requested a gun for trials without the troublesome automatic feed, adapted for single-round firing. A gun was duly despatched to HMS Excellenct, and in July 1940 the Rolls-Royce 40 mm was introduced into service as the 2-pounder Mk XIV. Production was entrusted to the British United Shoe Machinery Co. of Leicester.

When early production guns were mounted on patrol craft, several fatal accidents occurred during gun drill. It was found that the action of the gun was so fast that when the round was fed into the chamber, some over-sensitive primers were set off before the action was locked, firing the round in an open breech a few inches from the gunlayer's head. Another cause for concern was that standards of maintenance on small craft could not approach those of RAF armouries, and the aluminium parts suffered from salt-water corrosion. The open breech problem was partially overcome by slowing down the action, and when a modified feed was introduced the Navy ordered a further batch of the weapons.

In the same month that the modified gun under went sea trials, the Air Staff issued a requirement for an airfield defence system using a mobile heavy-calibre gun. Mr W A Rowbotham of Rolls-Royce's Experimental Department mounted on of the guns on a 15-cwt Chevrolet truck, with hydraulic rotation and elevation control. When test firing commenced, the vehicle started to vibrate and rock violently, and when further improvements were specified, such as armour for the crew, the project was sidelined. Meanwhile, a second more urgent order had been issued for an airborne anti-armour weapon to be mounted in Hurricane aircraft, and competitive trials were to take place between the Rolls-Royce gun and the Vickers Type S 40 mm weapon. A modified version of the Rolls-Royce was prepared, and during the test firing Walter Hampton, who was in charge, upset the LMS Railway Company. The test gun was being fired in the usual manner - from behind a brick wall, using a lanyard tied to the firing mechanism, with the gun rigidly secured. A long burst was fired, and the shells all struck the same spot, the later shells hitting the mass of solid shot and ricocheting. A goods train at Sinfin Moor suddenly screeched to a halt and its driver came runnig across the fields to the butts. When he got to within shouting distance, he brandished a missile and screamed, 'how about this, then?' It had come through the roof of his cab and narrowly missed him and his fireman! Walter told him that if nobody claimed it within seven days he could keep it! A strong protest was sent to the company and Hampton was told to be more diplomatic in future.

Mr G N Wallace of the RAF Gun Section supervised the test firing of the 40 mm guns for the A&AEE at the Pendine Sands test facility, where the Vickers weapon was found to be much superior. The Rolls-Royce gun was found to be adversely affected by altitude and temperature, and would not fire in an attitude of 80 degrees depression as required in the specification. Wallace duly recommended the adoption of the Vickers gun, which was fitted to the Hurricane Mk IID and proved to be an excellent weapon against all but the heaviest tanks in the Western desert. When Vickers had difficulty in supplying the required number of weapons, Rolls-Royce were given a production order for 1,000 of their guns, to be manufactured at BUSM, but during acceptance trials two guns had breech explosions after which deliveries were stopped. It was found that the cause of the explosions was the failure of a case in the ejector slot, so the slot was modified and trials continued. Extensivie firing tests proved that the gun was now much improved. Considering the relatively short development period. Viale's team had been remarkably successful in bringing a gun incorporating many new and untried features to a standard where it was passed as fit for RAF service by the Boscombe Down evaluation team. However, production was limited to parts for 200 guns, after which production ceased at Leicester. No further orders were received for either the Rolls-Royce or the Vickers Type S, as the emergence of rocket weapons promised to give the RAF a weapon which, when fired left the host aircraft with no heavy firing mechanism.

Details of the 40 mm Rolls-Royce gun

Calibre: 40 mm (1.57 in)
Action: Recoil-operated
Cyclic Rate: 120 rpm
Weight: 148 kg (328 lb)
Muzzle Velocity: 744 m/sec (2,440 ft/sec)
Ammunition Feed: Eight-round hopper
Number of Grooves: 12
Length of Barrel: 2,030 mm (80 in)
Length Overall: 2,870 mm (113.5 in)

The text and photos were taken from "British Aircraft Armament Vol.2: Guns and Gunsights", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 03 Mar 2003 16:27

Hi

The 57 mm (6-pdr) Molins No.1 Gun - Pt 1

The swift advance of the Panzer units in May 1940 revealed a lack of mobility as well as firepower in the the British 40 mm (2-pdr) anti-tank guns then in use. The Army proposed to mount much more powerful 57 mm (6-pdr) guns on small vehicles operated by a single crewman. Tis meant that the gun would have to be fitted with an automatic feed system. The design of this mechanism was entrusted to the Molins company, which was already working on abelt-feed unit for the Hispano gun. They received a development order on 14 February 1942, and most of the work was done by Desmond Molins, assisted by a Frenchman, Felix Ruau.

The rounds were stored in groups of four or five. When one group was fired, an electrical mechanism moved the next group sideways into position over the breech, thus the heavy shells were fed into the gund without links. When fully loaded, the magazine held 22 rounds. It was found necessary to modify variuos parts of the gun to enable the recoil to operate the magazine, and the modified weapon was officially known as the Molins gun. In August 1942 the prototype was taken to the nearby Deptford Shooting Club firing range, and with the assistance of Ordnance Corps experts it was fired automatically for the first time. It was then despatched to Woolich for exhaustive testing. Although the trials were succesful, the project was terminated owing to the appearance of the PzKpw VI Tiger tank, which was impervious to 57 mm (6-pdr) shells.

In early 1943 the Air Staff was discussing the replacement of the 40 mm anti-tank gun currently mounted on Hurricane Mk IID aircraft. The Molins seemed to be a logical weapon for a larger aircraft, so a trials team under G.F. Wallace carried out ground firing tests. The gun was found to be trouble-free, the only possible problem being the ability of the feed to operate under the stress of manoeuvres. The head of the department, Captain Adams, sent a favourable report to Air Marshal Sir Ralph Sorley, the controller of Research and Development. J.E. Serby of the Ministry of Aircraft Production then wrote to R.E.Bishop of de Havilland Aircraft regarding the possibility of arming a Mosquito with the gun. He was to bear in mind that the recoil force would be 3.628 kg (8,000 lb), and the weight of the gun and ammunition together could be 981 kg (1,800 lb). Bishop replied that the Mosquito could easily accommodate the gun - indeed in 1942 a feasibility study had been carried out for mounting a 94 mm (3.7 in) anti-aircraft gun.

A prototype installation was designed at Hatfield, and when the huge gun arrived for installation, Rex King of de Havilland asked when the horses would be coming! The gun was duly fitted in a written-off Mosquito FB Mk VI to confirm the effect of the muzzle blast on the wooden fuselage, and on 29 April 1943 five rounds were fired at the Hatfield butts. The blast shook the ground and left many ears ringing, and a cloud of dust showed that the solid shot had hit the aiming point. No damage had been caused to the airframe other than a sheared fixing bolt. Two days later the gun was installed in another Mosquito FB Mk VI to find the best method of attaching the gun and the auto-feed unit. The weapon was mounted 102 mm (4 in) to the right of the aircraft's centre line, with the muzzle protruding 610 mm (24 in) under the nose at a slightly downward angle and the recoil spring faired under the barrel. On 8 May a new Mosquito FB Mk VI, (HJ732), was wheeled into the experimental bay for conversion into the prototype Mosquito FB Mk XVIII (soon to be dubbed Tsetse fly). The massive gun and all its asociated electrical and cockpit controls were installed in four weeks, helped in no small measure by the easily adapted wooden structure.

The peaceful morning of Sunday 8 June 1943 was shattered when all 22 rounds were fired from (HJ732) in a staccato thumping burst into the sand. After further firing tests had been carried out, the aircraft was air tested. Air Marshal Sorley arrived at Hatfield on the same day to confirm that the Mk XVIII would be flown to Boscombe Down next day. He also announced that 30 of the next batch of Mosquito FB Mk VIs would be delivered as FB Mk XVIIIs, initially to be used by Coastal Command against U-boats in the western approaches of the Bay of Biscay.


The text and photos were taken from "British Aircraft Armament Vol 2; Guns and Gunsights.

Regards

Bob
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Postby Robert Hurst » 05 Mar 2003 11:38

Hi

57 mm (6 pdr) Molins No.1 Gun - Pt 2

When firing commenced at Boscombe Down it was found that the feed unit would not operate if the 'G' forces exceeded 2.5. Hundreds of rounds were fired during attempts to overcome the problem, but without success. On 22 June the machine was flown back to Hatfield where the charger arm and other parts were strengthened to overcome both positive and negative 'G' forces. Meanwhile, the second Mk XVIII was fitted with 408 kg (900 lb) of armour protection around the nose, to give the crew some protection against the armament of the U-boats. While 30 conversion sets were produced at Hatfield, Desmond Molins supervised the modifications to the feed, and by the end of June (HJ732) was back at Boscombe Down. During August it was extensively tested at Boscombe and Exeter. After 400 rounds had been fired, the undersurface of the starboard flap was torn off by the muzzle blast, and the flaps were therefore strengthened.

It was decided to retain the two outer 7.7 mm (0.303 in) Brownings, with double firing time from enlarged ammunition tanks, to discourage anti-aircraft gunners during the final stages of an attack. The empty 57 mm (6 pdr) cases could not be ejected overboard as they might hit the tailplane, so they were retained in the fuselage, where they could produce a loud clanging noise during manoeuvres. It was decided to use the Mk IIIa reflector gunsight rather than the larger Mk II because it gave a better peripheral view and had a dimming screen which minimised reflections off the surface of the sea. Alignment of the 57 mm (6 pdr) and the Brownings was achieved by using a central graticule for the former and a higher dot for the latter. As the rounds converged at 366 m (400 yds), the Brownings came to be used as an additional sighting aid for the big gun. As the pilots gained experience, moored targets were constantly hit during shallow diving runs, and rounds which fell short often ricocheted into the target.

By October, three Mk XVIIIs had been delivered to Boscombe with long-range tanks and armour, and were soon cleared for operations. Five crews from No.618 Sqn were posted to Predannack to work up on the new aircraft, along with 30 ground staff and armourers who had been trained on the Molins gun, by now officially entitled the 'Airborne 57 mm (6 pdr) Class 'M' Gun. Predannack was the home of the Beaufighters of No.248 Sqn, which formed a composite unit with the 'Tsetse' Mosquitos ranging over the Bay of Biscay. The first operation took place on 24 October 1943. Mosquitos (HX902 and HX903) searched unsuccessfully for enemy
shipping. On 7 November a U-boat was caught on the surface. After being hit by several shells aft of the conning tower, it submerged amid a cloud of black smoke. In December No.248 Sqn was re-equipped with the Mosquito FB Mk VI, and as a more FB Mk XVIIIs arrived, the strike force began wreaking havoc on German shipping in the Bay. Information from the broken Ultra code enabled the Mosquitos to intercept the U-boats en-route both to and from the Atlantic. The following combat report is typical.

Fkying Mosquito (HP922) we broke cloud at the prescribed time and position. I immediately observed a submarine proceeding on the surface with an escorting minesweeper. Whilst making my approach an escoring Ju 88 appeared in the sights. I pressed the gun button and the Junkers disintegrated. I then attacked the submarine which was seen to be hit.

About this time Admiral Donitz issued the followig directive: 'Owing to the damage caused by enemy aircraft mounting heavy-calibre guns, surface passage to port will only take place during the hours of darkness.' After a gruelling patrol, a journey through minefields at night was not appreciated by the submariners.

In February 1944 No.618 Sqn moved to Penreath, from where throughout the summer the Tsetse Mosquitos used their guns to good effect. On D-day (6 June) the squadron flew sorties from 0445 to 2215 hours protecting Allied shipping. On 7 June Mosquito (MM425) hit a submarine with 12 57 mm rounds; the U-boat dived amid a large patch of oil before one unfortunate crew member could get inside - he was last seen swimming in the general direction of America. By the end of August enemy activity in the Bay of Biscay lessened, and the squadron moved to Banff in Scotland. Attacks took place against German shipping and coastal installations in Norway, often up to six Mk XVIIIs leading the formation. The advent of more versatile rocket-firing Mosquitos restricted the production of the Mk XVIII to only 27, most of which served with No. 248 Sqn until the end of the war.

As with the early Hispano, it was found that AP projectiles were most effective, for they could penetrate a submarine's pressure hull and superstructure.

Details of the 57 mm (6 pdr) Molins Gun

Calibre: 57 mm (2.24 in)
Action: Recoil
Cyclic Rate: 60 rpm
Weight: 816 kg (1,800 lb)
Weight of Shell: 3.17 kg (7.1 lb)
Muzzle Velocity: 791 m/sec (2,600 ft/sec)
Ammunition Feed: Molins automatic feed
Magazine Capacity: 22 rounds plus one in breech
Sight: Mk IIIa dual graticule reflector
Length: 3.6 m (12 ft 5 in)
Height: 965 mm (38 in)

The above text and photos were taken from "British Aircraft Armament Vol.2: Guns and Gunsights", by R Wallace Clarke.

Regards

Bob
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