The Mauser BK-27 is a 27mm cannon fitted to the Tornado F3 and the Tornado GR4 aircraft for air-to-air or air-to-ground firing (and many other aircraft). The cannon is a single-barrel, high performance, breech cylinder gun operated by a fully automatic gas-operated system at a selective rate of 1000 or 1700 rounds per minute. The belted-link ammunition box is positioned to the side of the gun-feed mechanism and a floating buffer system imposes a very small recoil and vibration load on the airframe of the aircraft. Spent cartridge cases and empty links are ducted from the rear of the gun into a collection bay immediately behind the gun. Automatic ram air purges the gun compartment and spent cases bay during and after firing. The weapon has a very good hit-accuracy and one of its main strengths is the cannon’s ability to achieve a full 1700-rounds-per-minute rate of fire almost from the first round. This is an important asset, particularly if the cannon is being used against a fast-moving target. Targeting of the cannon is done through the aircraft’s head-up-display (HUD). When the cannon is selected in the cockpit, a firing predictor is projected onto the HUD; this depicts a moving line (continuously compacted impact line), or snake, that predicts where the next few rounds of cannon fire will go. The cannon can be aimed by using either a prediction sight or, in the case of the F3, a radar-designated sight. The cannon has a very high muzzle velocity and its high rate of fire, coupled with its ability to fire several different types of high-explosive shells, make it equally suitable for both interceptor-type aircraft and ground attack aircraft alike.
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