Handgun blanks
A blank is a cartridge which is primed and loaded with powder, but has no bullet. They typically instead have a wad in place to keep the propellant in the case (generally paper, plastic, or wool), or have the neck of the cartridge crimped shut. The latter is cheaper to do, but also slightly more dangerous since as the crimped neck unfolds there is a chance that pieces of brass will separate and become projectiles.
In its original use, a "blank" was what would now be called a practice round, typically with a wooden plug. These rounds were less-lethal but still potentially extremely dangerous, leading to the development of the modern form. Modern blanks can still cause injury or death if fired at very close range, particularly if they have a wad, or if there are obstructions (IE:Squib round, debris etc) in the barrel.
Standard blanks[]
Regular blanks are low-power cartridges used in situations where a report is desired from a firearm, but it is not desirable to launch a projectile: examples include military training and gun salutes.
Because a blank produces lower gas pressure and much lower recoil, a blank-firing adaptor (BFA) is often required to make the gun function normally. This is a pressure-boosting assembly attached to the gun's muzzle. Guns designed for high-powered loads (for example the SPAS-12 shotgun) sometimes simply cannot cycle blanks and have to be used as if they are manually operated.
Some guns, particularly starting pistols, are designed only for blank-fire. Blanks have also had some more unusual applications, including being used to ignite several WW2-era flamethrowers designed for cold-weather use.
Hollywood blanks[]
Blanks used in the film industry are usually "hot" loads, designed to produce a distinctive, exaggerated muzzle flash. Movie industry blank-firing adaptors are usually designed to be as unobtrusive as possible.
Commercial blanks[]
Manufactured for purpose built blank firers rather than actual firearms. Known examples are the 8x20mm Fiochi and the 9mm PAK.
Bulleted blanks[]
Previously mentioned as 'practice rounds'. Blanks that use a 'bullet' usually made of wood to use gas pressure to operate the weapon. These can be highly dangerous and require a muzzle device that severe the wooden bullet when leaving the barrel.
Grenade blanks[]
A grenade blank is a high-powered blank cartridge used to launch certain types of rifle grenade.