15-Inch Vickers Battery at Fortalesa Isabel II

Last summer I was lucky enough to visit the vast Fortalesa Isabel II which defended the port of Mahon, in Menorca. One of the fort’s most impressive sights is its huge 15 inch gun battery.

The Spanish island of Menorca, in the Balearic Islands, has a long and storied military history. The strategically important harbour of Mahon was historically the envy of the British, Spanish and French and was the reason for Fortalesa Isabel II’s construction. The for was the last major fortification built on the island, with the Spanish military beginning construction in 1850. A second phase of major improvements was made during 1853-1864. Work to improve and modernise the fort continued into the 20th century.

Fortalesa Isabel II main gate (Matthew Moss)
The ornate main gate of the fort, defended by a counterguard and rifle slits either side of the gate (Matthew Moss)

The Fortress is built on a beautiful rocky headland of La Mola at the mouth of the harbour and covers about a square kilometre. Construction was a massive undertaking and took over twenty years to complete, costing over nine million pesetas. The fortifications are some of the Mediterranean’s most impressive of the period.

The fort is a maze of tunnels, galleries, casements and buildings surrounded by a deep, dry moat. The fort’s first line of defence consisted of a moat 9 metres (30 feet) deep covered by rifle loop holes for infantrymen and embrasures for artillery. Interlocking fields of fire defend the landward approach to the fort’s main entrance, the Queen’s Gate.

Map of the La Mola peninsular and fort
Map showing the layout of the fort during the 19th century before the 15 inch guns were added (source)

Designed to dominate the entrance to the harbour the fortress was intended to hold 160 artillery pieces of various sizes, including Krupp guns and howitzers, many of these protected by strong stone casements. The fort’s armaments evolved overtime from muzzle-loaders to faster firing breech-loaders.

The Spanish continued to upgrade the fort’s guns over the decades mounting rifled guns and howitzers of various calibres ranging from 15cm to 30.5cm. In addition to the fort’s guns the defences also included mines in the harbour mouth and later a battery of shore launched torpedoes.

By the early 20th century the fort’s guns were increasingly obsolete against the backdrop of the naval revolution that saw Dreadnoughts come to dominate maritime warfare. With advances in naval architecture, armour and guns the Spanish government decided to purchase a number of massive 15 inch naval guns that could fire a 1,895 lb (860kg) shell up to 22 miles.

One of La Mola's 15 inch guns in position
One of the fort’s two 15 inch Vickers guns in position on Cape Espero (Matthew Moss)

Spain purchased 18 of these massive guns made by the British Vickers company, they had originally been designed for the cancelled Brazilian battleship Riachuelo. In Spanish service the guns were officially designated the Costa de 38.1cm Modelo 1926. During the 1930s the new coastal guns were installed on both the Spanish mainland and Menorca. Two guns placed in the Castillitos Battery, defending Cartagena, opened fire on a Spanish Nationalist fleet, during the dying days of the Spanish Civil War. While Menorca’s guns never fired a shot in anger, they acted as a deterrent.

The first guns reached Mahon in 1932, with a second arriving in 1936, these were mounted on the cliffs of Cape Espero on the La Mola peninsular. The guns were so huge they had to be transported to the fort on a specially built railway pulled by hand and traction engine. These formidable new guns brought Fortalesa Isabel II’s armament up to date, enabling it to protect Mahon from any modern warship.

15 inch gun being dragged by a traction engine through mahon
One of the massive 15 inch guns being pulled along its special track by a traction engine through the streets of Mahon (source)

The 15 inch (or 381mm) Vickers battery at the fort was positioned 70m above sea level and commanded the entrance to the harbour. Six guns were eventually sent to Menorca with two  placed on La Mola, two more installed in a battery at Favaritx (the remains of which can be seen here) in the north of the island and a pair at a battery near Llucalari in the south of the island.

While the guns at Favaritx were later removed, the guns at Llucalari remain. The fact that six of these massive and expensive naval guns were placed on Menorca shows its strategic value during the period.

Satellite photo of the 15 inch battery at Llucalari
Satellite photo showing Menorca’s other 15 inch battery at Llucalari (google maps)

The guns were mounted in barbettes which allowed the guns to traverse up to 300 degrees. The gun housing of the turret was armoured but while it would not protect the crew from a direct hit, it would protect against shrapnel. Below the guns were magazine stores for both cordite charge bags and projectiles, the machinery needed to rotate and move the gun and the motors to power it. Inside the turret were controls to open and close the breech, lift and lower the loading tray and aim the gun. The guns had a potential maximum range of 35km or 22 miles, however, the guns at La Mola lacked the necessary range-finding equipment to achieve this range.

Inside the 15 inch gun turret
A contemporary photograph showing the interior of the gun turret. A shell is sat on the loading try ready to be pushed into the breech. (source)

The ancillary buildings for the battery on La Mola are built just behind the two gun emplacements with offices, stores and barracks built in an old quarry. As well as the two main guns the battery was supported by four faster firing 6 inch Vickers guns.

15 inch Vickers gun firing in the 1980s
One of Menorca’s 15 inch guns firing c.1980s (source)

With the eruption of the Spanish Civil War in 1936, Menorca was initially held by the Republicans. But in 1939, the island fell to General Franco’s Nationalists and the fort’s military prison was used to house a number of prominent Republican prisoners. Throughout the Cold War the fort continued to be used by the Spanish Army as a training centre but the rise of air power, the invention of the cruise missile and nuclear weapons rendered the fort and its guns increasingly obsolete.

The last of Spain’s 15 inch guns were finally decommissioned in the mid-2000s, after nearly 80 years in service. Fortalesa Isabel II and her two massive guns never saw action, and today the site is maintained as an impressive museum which is well worth a visit.


Specifications:

Length: 18m or 59 feet
Weight: 86.9 tons
Action: breech-loading
Calibre: 15 inch or 381mm
Elevation -5 / +40 degrees
Traverse: 300 degrees
Rate of fire: 2 rounds per minute


Bibliography:

The Fortress of Isabel II on La Mola in Mahon Harbour (19th 7 20th Century), F. Fornals (2007)

The Conquests and Reconquests of Menorca, M. Mata (1984)

Guns of Cartagena, espele.net, (source)

‘Yo hice la Mili en La Mola de Menorca’, Facebook group with excellent contemporary photos (source)

www.fortalesalamola.com


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2018.

F1 Submachine Gun

The Australian military adopted the F1 submachine gun in 1962, with the first guns reaching troops in April 1963, it replaced the venerable Owen gun. Like the earlier Owen the F1 had a top-mounted magazine – a position that lent itself to prone firing and more comfortable carrying when slung. But it also shared some similarities with the British L2A3 Sterling.

NUI DAT, VIETNAM, 7TH BATTALION, THE ROYAL AUSTRALIAN REGIMENT (7RAR) with F1 SMG
Men of the 7th Battalion, The Royal Australian Regiment demonstrate the F1 to the Australian Army Minister, Malcolm Fraser, in Vietnam in 1967 (Australian War Memorial)

The F1 entered service alongside the Australian L1A1 (self-loading rifle/FN FAL), it shared the rifles butt plate and pistol grip – slightly minimising additional unique parts needed by the submachine gun. Australian Ordnance had begun searching for a replacement for the ageing Owen gun after the Korean War. The Owen had been made quickly and cheaply during the Second World War and while it was well liked by Australian troops it was felt it could be improved upon. Maintenance of the older Owen guns proved difficult as each weapon had been hand fitted to speed up production and some parts proved not to be interchangeable.

F1 SMG (Matthew Moss)
Left side view of an Australian F1 submachine gun, from the 1970 production run (Matthew Moss)

A number of designs were developed including one designated the Kokoda (presumably after the Kokoda Trail campaign fought by Australian troops in 1942). This design was lighter than the Owen but suffered from overheating problems. A series of designs from the Australian Design Establishment, designated the ‘X’ series, were then developed. These weapons incorporated elements from both the Owen and the British Sterling. Including the Sterling’s perforated barrel jacket and magazine and the Owen’s bolt, magazine orientation and forward pistol grip – a feature many troops with experience with both the Owen and F1 lamented to loss of with the adoption of the F1. The first two ‘X’ series weapons developed into the X3 which in 1962, after successful trials, became the F1.

8RAR with F1 SMG (AWM)
Member of 8th Royal Australian Regiment stood too with his F1 SMG (Australian War Memorial)

The F1 used a standard blowback action with a non-reciprocating charging handle. The charging/cocking handle was positioned on the left side of the receiver with its slot protected from the ingress of dirt by a dust cover. The F1 has a two-position fire selector with up for ‘safe’ and down for ‘fire’. The trigger mechanism allowed for firing single shots by pulling the trigger to the half-way point, this allowed the sear to trip into the semi-automatic position (see the diagram below).

Semi-Auto sear position in F1 SMG
Diagram from Australian Army Parts List showing how the F1’s semi-automatic mode works (source)

Chambered in 9x19mm, the F1 fed from a 34-round curved magazine, although it could use straight, single-feed, Sten or Owen magazines. In the 1960s, in order to achieve commonality with Britain and other Commonwealth nations, that used the Sterling Submachine Gun, the Australian government contacted the Sterling Armaments Company to enquire how much a license to produce Sterling’s magazines would cost, only to be quoted an exorbitant fee. The Australian government were unwilling to pay for the license and produced them anyway. And as Sterling could not afford to take legal action were able to continue to do so – with the understanding they would not sell any commercially. The Australian government would later purchase a number of suppressed Mark 5 Sterling-Patchetts, also adopted by the British army as the L34A1.

The weapon’s ejection port was located on the bottom of the receiver ahead of the trigger guard. A small piece of metal was added in front of the ejection port, as a hand stop, to prevent the operator from inadvertently moving their hand over the port. The F1 had an in-line stock fitting into the rear of the tube receiver. The sights were offset to the right, the rear peep sight folded against the receiver when not in use while the front sight, rather than over the muzzle, projected from the right side of the magazine housing.  The F1 could also mount the L1A1 self-loading rifle’s standard L1A2 sword bayonet.

Australian Sailors with F1 SMG
Australian sailors aboard the destroyer HMAS Duchess wait to take part in a live firing exercise with their unloaded F1 submachine guns, c.1969. (Australian War Memorial)

The F1 weighed just over 7lbs (3.2kg), was 28 inches long and had a cyclic rate of approximately 600 rounds per minute. It had a solid butt stock, unlike the Sterling which had a folding stock. The F1 was produced solely by the Lithgow Small Arms Factory with most sources suggesting 25,000 were produced for the Australian military between 1963 and 1973. The Lithgow Small Arms Factory Museum were kind enough to look into the exact number made for us, and reported that there is some uncertainty surrounding the exact number produced with production report totals varying, giving a total of either 21,916 or 24,828.

The F1s saw extensive service in Vietnam and later with Australian peacekeeping troops through to the 1990s. It was issued to rear echelon troops, ACP and aircraft crews and to infantry sections. While the F1 was appreciated for its reliability, for those troops who had experience with the venerable Owen Gun, the F1 lacked a certain something.  Colonel Warren Feakes noted that “every time I picked up an F1 I had the feeling that something was missing.” Another Australian veteran, Warrant Officer Kevin Konemann, who served in Vietnam in 1966-67, recalled: “It was awkward to fire from the shoulder and more awkward to fire from the hip” and that “the F1 wasn’t popular. Soldiers found it more difficult to point and bring on target than the OMC [Owen Gun] and firing from the shoulder… was decidedly more difficult without the front hand grip.”

Despite the shortcomings identified by some troops the F1 remained in service alongside the L1A1 self-loading rifle into the early 1990s, when both were phased out of use as the 5.56x45mm F88 (Steyr AUG) was adopted.


Technical Specifications:

Length: 28 inches (71cm)
Weight (unloaded): 7lbs (3.2kg)
Barrel Length: 8.35 inches (19.8cm)
Action: Blowback
Calibre: 9x19mm
Feed: 34 round box magazine
Cyclic Rate: ~600 rpm


Bibliography:

 

1966 Infantry Training Pamphlet, Platoon Weapons, Sub-machine Gun 9mm, F1, Australian Army, (source)

Repair Parts Scale, 9mm, F1 SMG, Australian Army, (source)

Vietnam ANZACs Australian & New Zealand Troops in Vietnam 1962-1972, K. Lyles (2004)

Military Small Arms of the 20th Century, I. Hogg & J. Weeks (1985)

‘Another Australian Native: The 9mm F1 Submachine Gun’, Arms & Militaria Collector No.21, pp. 53-56, I. Skennerton, (source)

Modern Small Arms, F. Myatt (1979)

The Owen Gun, W. Wardman, (1991)

F1 Sub-machine Carbine, Lithgow Museum, (source)


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2018.

TAB: Recommended Reading – The ArmaLite AR-10 by Joseph Putnam Evans

This is the first instalment of what will hopefully become a regular feature where we discuss some of the books we use when researching the guns we feature in our videos. We’ll give an overview of what the books cover, how they approach subjects and how good a resource they are.

With Vic’s recent special episode on the AR-10, I’ve been using Joseph Putnam Evans’ book ‘The ArmaLite AR-10: The World’s Best Battle Rifle‘ to help write the accompanying blog posts. While not without its flaws Evans’ book is without doubt the best published source on the AR-10 currently available.

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For many years the published material on the AR-10 was confined to both contemporary gun magazine articles on the ‘new’ rifle and a handful of retrospective articles published later. Very little was written about their surprisingly extensive combat use or even the nuances of the design changes. Even the Black Rifle books, also published by Collector Grade, lacked the context of where the AR-15 evolved from. ArmaLite AR-10 is well worth reading, and a great base for further research.

Hybrid Sten

 

During our first research trip last spring I had the opportunity to examine an unusual ‘hybrid’ Sten submachine gun. The weapon combined a MkII Sten’s receiver with a MkIII’s magazine housing. Added to this was a proprietary folding stock and a new fire control group and pistol grip.

Very little is known about the hybrid Sten with Peter Laidler’s book The Sten Machine Carbine mentioning it and the later Osprey book by Leroy Thompson sharing a photograph and brief caption which calls it an “experimental version of the Mk III.” It is also unclear exactly when it was built.

Below are some photographs I took of the Sten, lets look at some of the interesting features of the Hybrid Sten.

DSC_0807
left side of the Sten with the stock folded flush under the receiver (Matthew Moss)

No production Variant of the Sten was fitted with an under-folding stock, the Australian Austen, however, directly copied the MP38/40. The entire weapon is covered by a layer of textured, crackle paint finish, this was commonly used on commercial Sterling Mk4 submachine guns. The weapon has a short, 3.5 inch, perforated fore-end welded onto the front of the tube receiver that appears to be from a Lanchester.

DSC_0803
Rear right of the weapon close up of its pistol grip, stock and trigger housing (Matthew Moss)

The under folding stock is rudimentary but effective, the butt plate swivels free but the lock up is quite secure. It uses the receiver main spring-loaded return-spring cap. The folding stock attaches to the pistol grip assembly (which can be seen detached below).

The proprietary rectangular trigger group housing brazed onto the tub receiver is unlike any other Sten and lacks a fire-selector.

DSC_0811
Left side of the Sten with its pistol grip and stock assembly detached (Matthew Moss)

The pistol grip itself is made from paxoline, a form of early resin plastic. The shape shape of the pistol grip does not resemble any production or prototype Sten grip. A simple hand-stop, made from a bent piece of sheet metal, has also been added in front of the weapon’s ejection port to prevent the user’s hand moving back and fingers being caught if gripped by the forend.

DSC_0802
Right side of the Sten with its stock unfolded (Matthew Moss)

While the origins of the hybrid Sten remain unclear I don’t believe it was an officially made prototype. While impressive it is relatively crudely assembled and does not match the Sten prototypes made by Enfield, such as the VI. Intriguingly, the magazine housing of the weapon has been stamped ‘PILOT’ below the usual ‘STEN MkIII’ stamp. I suspect that the weapon may have been put together by a unit armourer, perhaps authorised by a superior officer to suggest improvements or as an unofficial project gun.

UPDATE:  Their is some evidence emerging that this Hybrid Sten may be related to the T42 Sten prototype, part of the Sten MkIV development program. Where this hybrid fits into the story is not yet clear but the similarities are striking, when we have more information we will revisit this weapon.

Technical Specifications:

Length (with stock folded): approx. 40cm (30in)
Weight: approx. 3kg (7lb)
Barrel Length: 16cm (6.5in)
Action: Blowback
Calibre: 9x19mm
Feed: 32 round box magazine
Cyclic Rate: approx. 500 rpm


Bibliography:

The Sten Machine Carbine, P. Laidler (2000)

The Sten Gun, L. Thompson (2012)


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2018.

Heckler & Koch HK53

In 1968 Heckler & Koch launched the HK33, chambered in 5.56x45mm, to compete with Colt’s AR-15/M16. The HK33, and later HK53, used the same roller-delayed blowback action developed for the G3 in the mid 1950s. However, few major contracts were forthcoming with the German military opting to continue using the 7.62x51mm G3.

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Heckler & Koch HK53 (with ‘navy’ lower reciever) brochure c.1987 (source)

Due to the modularity of the HK33′s design users could replace the butt of the standard rifle with a collapsible telescopic metal stock. H&K also subsequently designed a carbine version of the full-length HK33, the HK33K with a telescopic metal stock and 12.7 inch barrel. In the mid-1970s H&K began development an even shorter version. The result was essentially an intermediate calibre submachine gun similar to the Colt Commando and the Soviet AKS-74U. H&K designated this new weapon the HK53, it used the same telescopic stock as the HK33K and MP5 and a cut down 11 inch barrel, the HK53 also utilised a polymer forearm similar to the MP5s.

1
Contemporary promotional photos dating from 1985 (source)

Like the HK33, the HK53 fed from 25, 30 or 40 round box magazines. The weapon weighed just over 3kg (7lb), almost a 1 kg less than its parent rifle the HK33. Unlike the HK33, the HK53 has a four prong flash hider. A number of police forces and militaries adopted the HK53 for a variety of roles. Special forces units around the world including the British SAS, Royal Military Police Close Protection Unit and Royal Marines, designated the L101A1 in British service, who typically used it during close protection duties and operations involving close quarter battle.

2
Contemporary promotional photo dating from 1985 (source)

As shown in various MoD Equipment Failure Reports dating from the early 1990s the HK53’s in British service suffered from repeated damage and failure of the carbines’ locking rollers. This issue arose when using a number of different ammunition types including brass cased blank ammunition (H&K recommend the use of their proprietary blank cartridges). Following a meeting between the Army Technical Support Agency’s Directorate of Engineering and H&K a new design for the locking pieces were developed. These changes “increased the roll of blowback force during the unlocking phase… in turn this will reduce the mean energy of the recoiling mass of breech block and carrier” this was intended to reduce bolt bounce. The Royal Military Police Close Protection Unit’s L101A1’s were also fitted with a new two stage buffer within a fixed stock.

DSC_0843
HK53, stock collapsed, (Matthew Moss)

Due to its short length the HK53 also found itself pressed into the port-firing weapon role. Designated the HK53 MICV in this role the foregrip and stock was removed and a specially designed endcap and a spent case bag could be attachment. During its service life the HK53 went through a series of changes to furniture mouldings, buttstock types and fire selector options. It remained in production into the early 2000s, when Heckler & Koch replaced the HK33 and HK53 with the G36 and G36K.

Technical Specifications (from 1987 H&K brochure):

Length (with stock extended): 76.5cm (30in)
Weight (collapsible stock, unloaded): 3.35kg (7.4lb)
Barrel Length: 22.5cm (8.5in)
Action: Roller delayed blowback
Calibre: 5.56x45mm
Feed: 25, 30, or 40-round box magazine
Cyclic Rate: approx. 700 rpm

 


Bibliography:

The World’s Assault Rifles, G.P. Johnston & T.B. Nelson, (2010)

Heckler & Koch HK33 & HK53 manual (source)

HK53 factory colour brochure, 1987, (via Small Arms Review Reference Library)

Itemised list of L101A1’s which suffered damaged locking rollers, MoD Equipment Failure Report, 15 Nov. 1994, (via Small Arms Review Reference Library)

Army Technical Support Agency report on receiver damage to HK53 and G3 rifles, 1996,(via Small Arms Review Reference Library)


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2018.

FAMAE PAF Submachine Gun

The 1960s and 70s saw Chile was racked by political turmoil with a military junta, led by General Augusto Pinochet, taking control in September 1973. Pinochet’s Junta took control of the country via a bloody coup, overthrowing President Salvador Allende, and as a result all export of small arms from Britain to Chile ceased. In the early 1970s, before the coup d’etat, The records of the Sterling Armaments Company show Chile purchased an example of the company’s Mk4 submachine guns and no less than 101 suppressed Mk5 Sterling-Patchetts.

With the import of small arms from the UK and other countries banned by an embargo Chile’s government were eager to increase their self-sufficiency.  As a result in the mid-1970s the state-owned firearms manufacturer Fábricas y Maestranzas del Ejército (FAMAE) experimented with copying the Sterling Mk4 in an effort to minimise development costs.

DSC_0162
Left-side view of the PAF with its stock extented (Matthew Moss)

The resulting 9x19mm submachine gun was dubbed the PAF or ‘Pistola Ametralladora FAMAE’. It took the basic Sterling design and simplified it. The PAF lacks the Mk4’s perforated barrel jacket and instead has an exposed barrel, tipped with a rudimentary spoon-shaped compensator. It also lacked the Sterling’s folding stock, instead it had a simple collapsing stock. As a result, the disassembly catch has been moved 90-degrees to the left side of the receiver.

DSC_0163
Right-side view of the PAF (Matthew Moss)

Like the original, the Chilean copy retained the dirt-clearing grooves cut into the weapon’s breech block. The PAF’s plastic charging handle and butt stock shape are reminiscent of the Heckler & Koch MP5 – although much cheaper feeling in quality. The profile of the PAF’s pistol grip is slightly different but the weapon still fed from standard 34-round Sterling magazines. Interestingly, unlike the Sterling’s screwed-in-place barrel, the PAF’s was held in place by a machined barrel nut – in terms of production this is a much simpler system, no doubt borrowed from the Uzi.

The Chilean copy weighs significantly less than the British original, 2.5kg (5.5 lbs) and reportedly has a much higher 800 rounds-per-minute rate of fire. In general the PAF looks much like Sterling’s own later Para Pistol model, the Mk7.

Some sources suggest that only a small number of toolroom prototypes were made, although the relatively high serial number, #00748, of the example we looked at may indicate a limited production run may have been produced. It is clear, however, that the PAF did not go into general production. Instead, FAMAE later focused on weapons derived from Swiss small arms including the SIG SG 510 and SIG SG 540, and the SAF submachine gun introduced in the 1990s.

Note: The PAF was the last weapon we filmed during this particular research trip and we did not have time to film or photograph the PAF’s internals (we filmed a lot of videos that day and were pressed for time). Rest assured if and when we get the opportunity we will update this article with photographs of the weapon disassembled!  

Technical Specifications:

Length (with stock collapsed): approximately 44cm (17in)
Weight (unloaded): 2.5kg (5.5lb)
Barrel Length: 17.5cm (6.9in)
Action: blowback, open bolt
Calibre: 9x19mm
Feed: 34-round box magazine
Cyclic Rate: suggested ~800 rpm


Bibliography:

The Guns of Dagenham, P. Laidler & D. Howroyd, (1995)

‘The PAF: Chile’s First Indigenous Submachine Gun’, TFB, R. Olive (source)


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2018.

M45 Quadmount

 

Matt recently had the opportunity to visit the excellent Menorcan Military Museum at Es Castell, on the Spanish Balearic Island of Menorca. The museum is well worth a visit with some very rare and extremely interesting weapons on display. 

M16
An M45 mounted on a M16 half-track during World War Two (source)

The M45 Quadmount was developed by the W.L. Maxson Corporation for the US Army. It mounted four .50 calibre M2 Browning Heavy Machine Guns on a lightweight, rotating powered mount.  I recently had the opportunity to take a closer look at an M45 while visiting the Menorcan Military Museum.

Introduced in 1943, the M45 was capable of 360 degrees of rotation and 90 degrees of elevation. It was manned by a three man crew: two loaders, who loaded the M2 Browning’s 200-round belt drums, and a gunner.

The M45 was extremely versatile and could be mounted on a number of trailers and vehicles including the M20 and M17 trailers and the M16, M17 and M51 half-tracks.

M45 TM
Diagram from the M45’s manual showing the layout and some of the Quadmount’s parts (source)

The gunner sat on a canvas seat inside the M45, between the two pairs of guns. He controlled the aiming of the guns with two control handles and aimed the M45 through a reflex sight which was mounted to a sight bar.

The M45 was powered by two 6-volt batteries and weighed approximately 2,400lb (1,090kg). The gunner was protected by an armoured plate at the front with two hinged armour plates either side of the M1X reflex sight. The M45 mounted four M2 TT (Turret Type) varriant machine guns – these were fired by solenoids. All four of the guns could be fired at once but gunners normally alternated between the upper and lower pairs in order to allow the guns to cool and loaders to replenish the drums.

US_Army_M16_MGMC_AA_Half-track
An M45 mounted on an M17 half-track during the Korean War (source)

When all the guns were fired together the M45 had an impressive rate of fire of approximately 2,300 rounds per minute. The Quadmount saw action throughout World War Two, the Korean War and in Vietnam. However, with the beginning of the jet age the M45 became increasingly obsolete in the anti-aircraft role. It continued to be used against ground targets with many mounted on vehicles to create ‘gun trucks’.