page_title: Bofors 40 mm gun
section_title: Naval versions
hierarchical_section_title: Bofors 40 mm gun / British versions / Naval versions
caption_attribution_description: English: 40 mm Bofors AA guns on the Polish destroyer ORP Błyskawica Polski: działka plot 40 mm Bofors na ORP Błyskawica
context_page_description: The Bofors 40 mm gun, often referred to simply as the Bofors gun, is an anti-aircraft autocannon designed in the 1930s by the Swedish arms manufacturer AB Bofors. It was one of the most popular medium-weight anti-aircraft systems during World War II, used by most of the western Allies as well as some captured systems being used by the Axis powers. A small number of these weapons remain in service to this day, and saw action as late as the Persian Gulf War.
  In the post-war era, the original design was not suitable for action against jet-powered aircraft, so Bofors introduced a new model of significantly more power, the 40 mm L/70. In spite of sharing almost nothing with the original design other than the calibre and the distinctive conical flash hider, this weapon is also widely known simply as "the Bofors". Although not as popular as the original L/60 model, the L/70 remains in service, especially as a multi-purpose weapon for light armoured vehicles, as on the CV 90.
  Bofors has been part of BAE Systems AB since March 2005.
context_section_description: 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 western Europe 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 can be confusing 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 "stabilized tachymetric anti-aircraft gun" (STAAG) 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. The final version of STAAG was fitted to the RN Type 12 Whitby anti-submarine frigates and the Type 41/Type 61 diesel frigates completed 1956–1958. HMNZS Royalist was also fitted with STAAG Mk 2 during modernisation, completed in 1956. Initially it had three STAAG CIWS, the STAAG in Q position was removed in 1960, but it carried two mounts until the end of its service in South East Asian waters, in 1965. The crew of Royalist appeared to find the STAAG a reasonably effective and impressive anti-aircraft weapon during Operation Musketeer in 1956, off Egypt.
caption: Twin Bofors 40 mm aboard ORP Błyskawica, a WWII destroyer of the Polish Navy.
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