The Rolls Royce Experimental Machine gun

Today the Rolls Royce Company is synonymous with high quality luxury cars. However, during World War 2 the company produced some of the best and most innovative military technology of the day. Trucks right? No, how about experimental heavy machine guns.

The armament of Rolls Royce

Founded in 1904, the Rolls Royce Company has carried out several defense contracts over the years. During World War 1, some 120 Silver Ghost luxury cars were converted into some of the first armored cars in military history. With the addition of a machine gun and later a Boys Anti-tank rifle in an armored turret, these cars served in both world wars.

Besides armored cars, the company also produced massive piston engines for fighter planes. The legendary Rolls-Royce Merlin engine powered thousands of Allied aircraft used during World War 2 including the RAF Spitfire, and the P-51 Mustang. To this day, the company continues to manufacture high technology military power plants for combat jets, armored vehicles, UAVs, and helicopters.

The Rolls Royce Experimental Machine gun

When World War 2 erupted, most of the machine guns mounted in British RAF fighters and bombers were short-ranged .303 Enfield caliber weapons and it soon became clear that a larger caliber weapon would be useful to engage targets more effectively and at longer ranges. The US-designed Browning M2 “Ma-Deuce” with its huge .50-caliber (12.7x99mm). It was and remains popular on this side of the pond, but it is admittedly quite heavy at over 80-pounds in its lightest version. Worse, it has a relatively low rate of fire. Rolls Royce, in 1941, decided to see what they could do to fix that.

A RR engineering team led by Dr. Spirito Mario Viale designed a .50 caliber recoil-operated weapon that fired from a locked breech similar to that of the Swedish Friberg-Kjellman machine gun, thus forgoing traditional gas-operation to save space and weight. They then constructed the body and breech cover out of a super light RR50 aluminum alloy. The barrel was designed to be five inches shorter than the M2. A special wedge-shaped balance-piece extended and retracted the striker pin. Overall, the design came in at a weight 42% less, not to mention a foot shorter, than the venerable Browning M2HB. And the Rolls gun nearly doubled the cyclic rate of the M2.

Comparison specs:

The RR gun

Length: 50.50inches (1270mm)

Weight (Unloaded) 49lb 0oz (22.22kg)

Barrel: 40.00inches (1016mm), 6 grooves, right-hand twist Cyclic Rate: 1000rds/min

Browning BMG M2 (HB air cooled version)

Weight (Unloaded) 83.78 lb. (38kg)

Length (OA): 65.2 inches (1,656 mm)

Barrel length: 45-inches (1,143 mm)

Cyclic Rate: 450-575 rounds per minute.

Abandonment

The prototype, promising on paper, was tested at Pendine Sands in March 1941 and immediately revealed issues. The extractor, similar to that used on the Degtyarev type light machine gun, was problematic and suffered breakages. The shortened barrel also produced an immense muzzle flash (as should be expected from a locked breech machine gun that fired 1000 .50-caliber rounds a minute!) A five-inch long flash suppressor was promptly fitted. Coincidentally (or perhaps not) this gave the weapon the same length barrel as the M2.

Rolls, with the Ordnance Board’s blessing and 2000 rounds of test ammunition, began work on modifying the design to fire the even more robust .55-caliber (13.9x99mmB) Boys Anti-tank round. However, by 1942, all further research was shelved and the gun faded into the history books. It is likely that by that time, with thousands of ‘good enough’ M2s available via Lend Lease, the new gun was not needed. Even the promise the Rolls gun showed as an airborne antitank cannon was a moot point as lightweight 20mm and 40mm cannon took to the air. In a twist of fate Dr. Viale’s team helped to design a 40mm airborne cannon for Rolls Royce in 1943, but that is another story.

Today the M2 soldiers on as a standard 12.7mm NATO weapon around the world. In 1949, the Soviets introduced their KPV heavy machine gun in .57-caliber (14.5×114 mm) that replicated what would have been the final Rolls product by firing an anti-tank round at machine gun rates.

Meanwhile, the sole example of Roll’s experimental aluminum machinegun weapon resides as Record No. PR.1744 at the UK’s National Firearms Centre- The Royal Armouries Museum in Leeds, England. Next time you are in the area in your Silver Ghost or Spitfire, stop on by and check it out.

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