Rheinmetall Borsig Mk108
The Rheinmetall Borsig Mk108 cannon, better known as the "Pneumatic Hammer" due to it's distinctive firing sound, was the main weapon of the Me 262. Four of these weapons were fitted in the nose of the machine, and could be fired in banks of either two or four simultaneously. With a rate of fire of about 11 shells per second. The destructive power of these four 30 mm cannon was nothing short of incredible. Since the "mine shells" used in the Mk108 exploded on impact, only a quick burst was needed to bring down a large four engined bomber.
The only drawback to the Mk108 was the low muzzle velocity of the weapon (1890 km/hr). This meant the shells traveled slower than in similar large caliber weapons. In the Me 262, the pilot had to use careful timing to fire at precisely the right moment. The speed of the Me 262 often made this difficult, as an enemy target might only be in position for a split second. Compared to the rapid firing spray of US .50 machine guns used in American fighters, the Mk108 was like firing a rifle shot.
The Borsig was developed as a private venture around 1940, and was electrically operated, with pneumatic (compressed air) triggering/resetting of the breach. The Mk108 also were used on variants of the Bf 109 and Fw 190.
The view to the left shows a rare glimpse into the removal of the nose section of an Me 262. The electrical firing systems and bulkhead assemblies, including the forward bulkhead, through which the cannon barrels protruded into the outer skin apertures are visible. In the bottom right of the picture are the spent cartridge chutes which exit towards the underside of the pack. The two reinforcing rods can clearly be seen at either side of the cannon, towards the top of the photograph.
The Mk108 cannons were fired by thumb and index buttons on the control stick. The stick had a unique safety device that would flip up and around to expose the top thumb button (B Knopf) and form the index button trigger (A Knopf). Each button fired two of the cannons, the A button the upper cannons and the B button the lower cannons. On some aircraft the A button fired all 4 cannon. The button on the upper right side of the grip (C Knopf) would release the bombs. (C Knopf) and on the lower front is the radio transmit button. The large button (Druckladung Knopf) on the lower left side of the grip is for cycling the breechblock in case of a jam or dud round.
Above images were used with express permission of Classic Publications