It CAN be done with any gun which uses modern cartridges (which are sealed), but it is EXTREMELY dangerous to do, and absolutely SHOULD NOT be done. Attempting it may result in injury or death to the firer.
yah because it contains saltpeter which releases oxygen when ignites. I have my doubts but you can fire a gun underwater. But don't try it as it could explode the gun barrel. And if it doesn't rupture the gun the first time you try it, then it could explode the next time you fire it even out of water.
It didn't replace any gun, it was the first rapid fire weapon to be made.
Not if it depends on combustible gas.
aim good
When the short & wad do not exit the barrel when fired, you have a squib fire, on any gun.
You might possibly be able to get it to fire, but you should never try to fire any ammo from any gun other than what it's designed to fire or what the manufacturer says it will fire. It might damage the gun or hurt the shooter.
Any gun store or major retailer should carry a fire proof gun cabinet. Also you might be able to find one in stock at amazon.com.
light a match underwater and let it burn
There is sort of two answers. Some guns can fire if dropped, however, any modern, properly designed gun will not fire if dropped, unless there is some sort of mechanical problem.
dry fire it without any BB's
You don't do it any good.