Today we're looking at a few rare examples of the Soviet designed 4.5x40R and 5.66x39mm rounds. These are specifically made to be used in underwater weapons, with the 4.5x40R fired out of the SPP 4 barreled pistol, and the 5.66x39 fired out of the APS underwater rifle. Both of these rounds fire a large steel dart, which is supercavitates through the water, using its length to stay stable.