Bofors 40 Mm - British Versions - Naval Versions

Naval Versions

The Royal Navy also made extensive use of the Bofors. Their first examples were air-cooled versions quickly adapted to ships during the withdrawal from Norway. With the fall of the west in 1940 the Dutch mine-layer Willem van der Zaan brought them their first example of a water-cooled gun on their Hazemeyer tri-axially stabilized mounting. Locally produced examples started arriving in 1942, known as the QF 40 mm Mark IV for use in twin-mounts, or the QF 40 mm Mark V for single mounts. The Navy ran through a variety of versions of the basic Bofors gun over the war, including the Mark VII to Mark XI. The Royal Navy's home-grown light anti-aircraft weapon, the QF 2-pounder gun, also had a caliber of 40 mm, but was referred to as the QF 2 pdr.

The designation of models in Royal Navy service is confused as the gun and its mounting received separate mark numbers. The following mountings were used;

• Mark I: twin mounting based on American design and using American built guns, not widely fitted. Fitted for remote fire control.
• Mark II: quadruple version similar to Mark I
• Mark III: a navalized version of the Army single mounting, hand worked elevation and training.
• Mark IV: a tri-axially stabilized twin mounting copied from, and usually known as, the "Hazemeyer". It had on-mounting fire control, and was usually fitted with Radar Type 282 to provide target range information.
• Mark V: twin mounting, that superseded and eventually replaced the Mark IV, often referred to as the "utility" mounting. This was a simplified, unstabilised mounting based on the American twin mounting Mark I, and was designed for remote fire control.
• Mark VI: a six-barreled weapon feeding from large trays instead of clips and designed for remote control from a dedicated radar-equipped director.
• Mark VII: a single barreled, hydraulically powered mounting that superseded the Mark III and entered service in 1945.
• Mark IX: Mark VII mount modified to electrical power, as the Mounting Mark IX, and in this form saw service in the Falklands War.

The Mounting Mark V (Mark VC for Canadian built examples) for the 20 mm Oerlikon and QF 2 pounder guns was also adopted initially as an interim mount for the Bofors. It was a single barreled mounting with hydraulic power, and was known as the Boffin.

The final British Bofors mounting that saw service was the STAAG (Stabilized Tachymetric Anti Aircraft Gun') which was twin-barrelled, stabilised, and carried its own tachymetric (i.e. predictive) fire control system, based around the centimeter Radar Type 262, capable of "locking on" to a target. This mounting was heavy (17.5 tons) and the high-vibration environment of the gun mounting was poor location for sensitive valve electronics and mechanical computers. STAAG Mark I carried the radar dish over the gun barrels where it was subject to damage during firing, therefore STAAG Mark II shifted the set to the roof of the control cabin. STAAG was ultimately too difficult to maintain in the harsh environment of a warship and was later replaced by the Mounting Mark V with the fire control equipment located remotely, the single Mark VII and ultimately, with the Sea Cat missile.

Visitors to HMS Belfast, moored as a museum ship in London, can manually traverse and elevate a twin Bofors mounting.