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Blank cartridges, as used in nail guns

Yugoslavian 7.9 mm (7.92 x 57 mm or 8 x 57 Mauser) blank cartridges.

A blank is a type of cartridge for a firearm that contains gunpowder but no bullet or shot. When fired, the blank makes a loud flash and report.

It should not be confused with a dummy, which does not contain gunpowder, and is completely inert.

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, in movies that require gun fights, and in starter's pistols to signal the beginning of races. 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 for long enough to cycle the firearm's action. 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. The 5-in-1 style of blank is also commonly used for dramatic effect in real firearms, as it is designed to cycle through firearm actions and fit a variety of firearm chambers.

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 rifle grenades, though some types of grenades are capable of trapping the bullet of a live round. Blank rimfire cartridges, commonly called power loads, are also used in some nail guns, where the power is tapped to force a heavy piston into the nail, with enough force to bury its full length in steel or concrete. Larger blanks are also used in line launching guns, such as the line launching kit for the Mossberg 500 shotgun.

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 several randomly selected shooters in an execution by firing squad. This is to allow the shooter to believe that they fired the blank. However, an experienced shooter would likely be able to detect the difference between the recoil of a live round and the less significant recoil of a blank cartridge, and thus would be aware as to whether or not they had fired a lethal round.

Given the explosiveness of blank cartridges, they are by no means safe. While blanks do not contain bullets, they often contain a paper or plastic plug that seals the powder in the case, called a wad (a term derived from shotgun shells). This wad can cause bruising at medium ranges and severe penetrating wounds at close range. There is also a great deal of hot, expanding gas that comes out of the muzzle of the gun when a blank round is fired. Exposure to this gas can cause grievous injuries (see powerhead for an example where this is used). In addition if there is any debris in the barrel (for example stones in the far end) it will be expelled at a similar velocity to a bullet, with similar capability for harm. Actors in particular are at serious risk of injury from blank cartridges used on movie sets. Actors Brandon Lee and Jon-Erik Hexum were both killed in accidents involving blank cartridges; Lee was killed by an old cartridge fragment lodged in the gun, while Hexum died when the wad from the blank fractured a piece of his skull, sending bone fragments into his brain. The explosion alone can cause damage to the eardrum. In the Army Cadet Force, the hazards of a blank cartridge are often demonstrated by 'shooting', at close range, a ration pack of sausage and tomato. The pack is ripped to shreds by the force of the explosion.

• World Fast Draw Association resource page, includes video instructions for loading blank cartridges for Fast Draw
• Definition of "movie" or "5-in-1" blank
• The ABCs of PATs, information on powder actuated tools and power load blanks