OK, here goes why 50 is probably the ideal speed. First of all, you want to be as fast as possible, because the game ignores all inputs until the gun is allowed to shoot again. The faster the sps, the closer together the trigger pulls are, and the sooner a trigger pull will happen after the gun is ready to shoot again. Since 50 is the fastest available in the custum editor, it is the ideal viking speed by this theory. Another reason that 50 is ideal is that the burst guns shoot every 0.2 seconds. Since you need 5 0.2 second times to make one full second, and 50 is a multiple of 5, it should hae a trigger pull falling exactly on each 0.2 second ending. By this reasoning, any multiple of 5 should work well. The one problem here is that the gun might not shoot when the trigger is pulled exactly on the 0.2 second interval, so the other theory comes into affect. Basically, 50 should work great, but 5 might work just as well... I would not go with say, the 666 from intensafire, because it is not a multiple of 5, and I doubt it is actually 666 anyways.