Ordnance BLC 15 Pounder - History

History

Many modifications were made to the old 15 pounder barrels to adapt them to a new carriage with a recoil buffer and recuperator above the barrel similar to the modern 13 pounder design. Previously the barrels had been mounted directly on the carriage by trunnions. Now the barrel was suspended from a forged-steel inverted U-shaped cradle which had trunnions to attach it to the carriage. The trunnions, sight brackets and elevating gear attachment lugs were removed from the barrel. The radial T-vent hole on top was plugged, holes in the jacket passing through the trunnion centres were sealed with screwed steel plugs, and the holes in the hood for fitting tangent sights were plugged with white metal alloy.

The 3-motion breech was replaced by a single-motion interrupted screw breech which had an axial T vent running through it into the chamber, designed to take a T friction tube.

The new firing mechanism involved a new "push" type T friction tube which was inserted into the axial breech vent. The crosspiece of the T was positioned pointing upwards. A long layer's guard was added to the left side of the cradle projecting behind the breech. A spring-loaded firing handle was built into the layer's guard. When cocked by pulling back and then released, it sprang forward and struck a firing lever on the breech, which translated the forward motion to a downward motion and propelled a firing plunger into the T of the friction tube which in turn ignited the cordite propellant charge.

In 1915, Territorial batteries guarding the east coast of England adapted their 15 pounders for use against Zeppelins, by simply digging a pit to accommodate the trail of the gun, to allow it to be trained upwards. It is unlikely that this arrangement was ever used operationally. In a more sophisticated adaptation, two 15 pounders were modified for anti-aircraft use by increasing allowed elevation to more than 60°. These guns were installed at Ford Wynyard in Cape Town.