Bofors 40 mm Automatic Gun L/70

The Bofors 40 mm Automatic Gun L/70, (Bofors 40 mm L/70, Bofors 40 mm/70, Bofors 40/70 and the like), is a multi-purpose autocannon developed by the Swedish arms manufacturer AB Bofors (today BAE Systems Bofors) during the second half of the 1940s as a modern replacement for their World War II-era Bofors 40 mm L/60 gun-design. It was initially intended as a dedicated anti-aircraft weapon, being sold as Bofors 40 mm Automatic A.A. Gun L/70, but has since its conception been redeveloped into a dedicated multi-purpose weapon capable of firing both sabot projectiles and programmable ammunition.

The 40 mm L/60 was introduced in 1932 and was a useful weapon for its era, being widely used among many forces and produced under license in several countries. The introduction of faster fighter-bombers and especially the widespread introduction of jet-powered aircraft in the post-war era severely limited its abilities. The L/70 was designed to improve both its operating range, to give it more time to respond to targets, and greatly increase its rate of fire to increase the odds of a hit. The most superficial changes are the longer L/70 barrel, double cooling vents on the jacket and the fact that the weapon comes chambered for a more powerful 40×365mmR cartridge (vs 40×311mmR for the L/60). The changes are minor enough that it looks similar to the L/60. Most important is the new ejection system which ejects the empty cartridge cases out from the opposite side to the feed, compared to the system on the L/60 which ejects the cases straight out the back of the gun. This system change almost doubled the mechanical rate of fire from the previous system. The operation is otherwise similar to the L/60, combining a self-ejecting gun with a recoil-operated autoloader in the same receiver.

The L/70 design never achieved the same popularity and historical status as the original L/60 design but has still seen great export and popularity to this day, having been adopted by around 40 different nations and even being accepted as NATO-standard in November 1953. It is still being produced and sold (since March 2005 by BAE Systems AB), and several variants exist for both field and naval applications. A notable variant is the Bofors 40/70B "light armored vehicle variant" which is in use on the Swedish strf 9040 and Korean K21 infantry fighting vehicles.

Despite the L/70 being a separate development to the older L/60 design, the similarities and success between the two guns has caused them both to be widely known simply as "the Bofors" or the "Bofors 40 mm gun", which at times causes the guns to be confused as one and the same weapon.