The Australians had a technique, using the thumb and index fingers to work the bolt, and slapping the trigger with the smaller fingers of the same hand, could put out their 'Ten rounds, rapid' in ten or twelve seconds. That was aimed fire for effect, minute of torso accuracies. In 1915 a German battalion walked into a smaller unit of Diggers and were decimated. The living put their hands up and surrendered. The German officers swore they were under machine gun fire.
I've tried the technique, it works fine, but I know I'm not as fast as those Australians were.