Lots of theory and guesswork. Most standard Military ammunition will work fine under water, though most automatic weapons will not - some will explode. The reason I know that most Military ammo works is that it is often used in power-heads used for killing sharks etc., when diving. I have had power-heads chambered for .308 Winchester, .223 Colt, .762 Nato and twelve gauge shotgun (SSGs). I have also seen a 9mm Browning Hi-Power explode when fired underwater. The distance traveled depends very much on the projectile. The Browning I mentioned was loaded with wadcutters, but full jacket with long tapered tips travel far enough and impact hard enough to kill gamefish.
http://www.waternsports.com/store1/i...HeadBiller.jpg