The British 3.45 in Mk 1 RCL Gun

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Robert Hurst
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The British 3.45 in Mk 1 RCL Gun

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Post by Robert Hurst » 21 Dec 2002, 12:48

Hi

The first 'Burney Gun' was a 20 mm single-shot gun, developed with a view to eventually turning it into an automatic cannon. It weighed 50lb and fired the standard Oerlikon gun shell at 3,500ft/sec, an improvemnt of 700ft/sec over the stabdard Oerlikon. But there was no requirement that the army could see, and no further work was done.

Next came a 3.45in gun capable of being fired either from a light tripod or from the shoulder; inevitably, from its calibre, it became known as the '25pdr Shoulder Gun', though in fact, the projectile did not weigh 25lb. In its original form (known as P1) it had a single nozzle attached to the downward-opening screw breech block, and a coned cartridge case with blow-out base. In October 1942, Sir Dennis Burney approached the Director of Artillery's Department to arrange official trials, and a brief demonstration given in the following month was, in the official word, 'promising'. During subsequent months, manufacture of 32 pilot models was begun by the Broadway Trust Company, a consortium of engineering firms organised by Sir Dennis to develop his armament inventions. In 1943, the Ministry of Supply set up their 'RCL Group' to undertake completion of Burney's designs to service standards, and the Armaments Design Department began work on a slightly different (P2) version of the 3.45in, which used Burney's other cartridge case design, a conventionally-shaped case perforated with a number of large holes in the wall, through which the gas was vented into an annular space around the gun chamber and then backwards through four jets arranged around the breech. In November 1944, the War Office stated a firm requirment for a number of these guns, with the intention of using them in the Far East, where heavy firepower from a portable weapon would be of great value. Unfortunately, trials showed up some problems, notably a variation between recoillessness and recoil due to erosive wear in the throats of the venturis, and before this could be cleared up and the guns put into production, the war was over. A total of 135 guns were eventually made, and most of them were issued to various units for extensive user trials in order to 'feel out' the user's reaction to such a novel weapon, but apart from this, the 3.45in RCL was never issued for general service.

Data: Ordnance, RCL, 3.45in Mk 1

Weight of gun and breech mechanism: 75lb
Total length: 68.55in
Length of bore: 50.874in (14.75 cal)
Rifling: 16 grooves, uniform RH 1/20
Breech mechanism: Interrupted screw, percussion fired, four venturis
Elevation: Free
Traverse: Free
Weight in action: 75lb

Performance: Firing standard 11lb Wallbuster shell

Muzzle velocity: 600ft/min
Maximum range: 1,000 yards

Ammunition:

Cartridge, RCL, 3.45in WB Shell Mk 1. This complete fixed round consisted of a cartridge case pierced with holes in the wall, and with a thin brass liner to protect the propellant, and a Wallbuster shell. The propelling charge was 1lb 2oz Cordite. The shell was filled with Plastic Explosive and carried the Base Percussion fuse No. 299. The weight of the complete round was 16.25lb

The above text and the accompanying photos were all taken from 'British & American Artillery of World War Two', by Ian V. Hogg

Regards

Bob
Attachments
3.45 in mk 1 rcl gun.jpg
3.45 in mk 1 rcl gun.jpg (41.02 KiB) Viewed 2675 times
3.45in heat round.jpg
3.45in heat round.jpg (22.96 KiB) Viewed 2675 times
3.45 in mk 1 recoilless gun.jpg
3.45 in mk 1 recoilless gun.jpg (32.35 KiB) Viewed 2798 times

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