Blank

Blanks are commonly used when the sound and flash of gunfire is needed, but a projectile would not be safe, such as in military training maneuvers or funeral honors, in movies that require gun fights, in starter pistols to signal the beginning of races and in the equestrian sport of Cowboy Mounted Shooting.
Blanks used by the military are usually used with a special blank-firing adaptor in the firearm that constricts the barrel, keeping chamber pressures from the blank high enough and for long enough of a duration to cycle the firearm's action. In case of non-crimped blanks, it also serves to pulverise the plug to prevent it leaving as a projectile.
For movie use, specially designed blank-firing firearms are often used, which increases the margin of safety as they cannot be loaded with live ammunition. 5-in-1 blanks are specifically made for theatrical use and are commonly used in real firearms for dramatic effect. 5-in-1 blanks can function in a variety of different calibers, hence the name.
Special blank cartridges are also used for applications where the explosive power of a cartridge is needed, but a projectile is not. Blank cartridges were commonly used for launching tear-gas or rifle grenades, though some types of grenades are capable of trapping the bullet of a live round. Larger blanks are also used in line launching guns, such as the line launching kit for the Mossberg 500 shotgun.

Blank cartridges as used in nail guns
Blank rimfire cartridges, commonly called power loads, are also used in some nail guns (powder-actuated tools), where the power is tapped to force a heavy piston into the nail, with enough force to bury its full length in steel orconcrete.
Some forms of fast draw competitions use special blanks that are loaded with a layer of slow burning rifle powder on top of a thin layer of faster-burning pistol powder. The pistol powder ignites the slower burning rifle powder, and fires it out the barrel much like a shotgun shell. The burning powder only travels a few yards before it completely combusts, but that is far enough to burst the balloon used as a target for those competitions. Wax bullets are also commonly used for competitions and training where a non-lethal projectile is required.
A blank cartridge may also be issued to a randomly selected shooter in an execution by firing squad, on the theory that each of the shooters may take comfort in the fact that they may not have fired a live round. This tradition dates back to before cartridge arms, when a muzzle loading musket would be loaded without a ball.[1][2][3]