The SaMaKa (Salvenmachinenkanonen) was a multi-mount Luftwaffe flak gun that held 8x 7.92mm MG-81s that fired 1,600 rpm EACH!!! So the total firepower of the weapon was 12,800 rpm- greater than anything postwar until the experimental Australian Metalstorm caseless weapons came along. The SaMaKa had one huge draw-back in that it consumed huge amounts of ammo and overheated fairly quickly... and yet in the airfield defense role, NOTHING Allied would get near that beast when they saw it fire. The single MG-81 GPMG was the fastest firing MG of the war at 1600 rpm, faster than the German infantry MG-42 which fired up to 1300 rpm depending on the bolt used. But whereas the MG-42 was an infantry weapon, the MG-81 wasa LW aircraft gun. Some were adapted for infantry, but they were rarely encountered. Amazingly, the Imperial German Army and LSK of WW1 had the experimental GAST guns by 1918 which were interconnected and also fired 1600 rpm!!! But time ran out and the Germans buried those. They were discovered in the early 1920s and destroyed...

SaMaKa: http://www.militaryimages.net/photopost/data/535/Samaka_GPMG_Mount.JPG