A blank-firing adaptor or blank-firing attachment (BFA), sometimes called a blank adaptor or blank attachment, is a device used in conjunction with blank

Blank (cartridge)

A blank is a type of cartridge for a firearm that contains gunpowder but no bullet or shot. When fired, the blank makes a flash and an explosive sound . Blanks are often used for simulation , training, and for signaling...

 ammunition. Blank firing adapters are required for allowing blanks to cycle most automatic firearm

Automatic firearm

An automatic firearm is a firearm that loads another round mechanically after the first round has been fired.The term can be used to refer to semi-automatic firearms, which fire one shot per single pull of the trigger , or fully automatic firearms, which will continue to load and fire ammunition...

s.

Design

The design of the blank firing adapter depends on the intended use. Different designs are used for different firearm action

Firearm action

In firearms terminology, an action is the physical mechanism that manipulates cartridges and/or seals the breech. The term is also used to describe the method in which cartridges are loaded, locked, and extracted from the mechanism. Actions are generally categorized by the type of mechanism used...

s and different user needs. For military use, BFAs are made obvious in order that they can be seen to be fitted - in addition to its role in cycling the action of a weapon, the BFA also prevents debris from the blank round (and in some cases, inadvertently loaded live rounds) escaping. This debris could cause injury to nearby personnel if the BFA has not been fitted or has fallen off. Use in motion picture special effects, however, requires the BFA to be hidden from casual view, so as not to disturb the illusion of live ammunition being fired, a feat usually accomplished with replacement barrels, the diameter of which is significantly reduced just in front of the chamber.

Gas operated and blowback firearms

BFAs for blowback

Blowback (arms)

Blowback is a system of operation for self-loading firearms that obtains energy from the motion of the cartridge case as it is pushed to the rear by expanding gases created by the ignition of the propellant charge....

 and gas-operated firearms are relatively simple. These weapons depend on high pressures in the chamber generated by the combustion of the propellant to push the breech block

Breechblock

A breechblock is the part of the firearm action that closes the breech of a weapon at the moment of firing....

 to the rear, allowing another round to be chambered and fired. If a blank round is used, there is no bullet to seal the barrel, and the combustion gases exit through the muzzle without building up enough pressure to rechamber the next round.

Simple BFAs for these firearms consist of a metal plug with screw threads. The adaptor is attached to the muzzle

Muzzle (firearm)

The muzzle of a firearm is the end of the barrel from which the projectile will exit.Precise machining of the muzzle is crucial to accuracy, because it is the last point of contact between the barrel and the projectile...

 of the firearm, and may attach to or replace the muzzle brake

Muzzle brake

Muzzle brakes and recoil compensators are devices that are fitted to the muzzle of a firearm or cannon to redirect propellant gases with the effect of countering both recoil of the gun and unwanted rising of the barrel during rapid fire...

 if there is one. A means is provided to allow some of the powder gases to escape. This can be adjustable, allowing it to regulate the amount of pressure used to rechamber the next round.

A drawback to the use of BFAs in gas-operated firearms is the amount of powder residue that builds up in the barrel. Since a limited amount can escape (compared to when live ammunition is in use, and a larger amount exits the barrel), the barrel can foul very quickly. Extreme care must be taken to ensure cleanliness of the barrel following BFA use to avoid damage to the weapon and injury to the operator due to fouling in the barrel.

Recoil operated firearms

Since blank cartridges generate very little recoil, far less than that produced by a live round, the recoil operation

Recoil operation

Recoil operation is an operating mechanism used in locked-breech, autoloading firearms. As the name implies, these actions use the force of recoil to provide energy to cycle the action...

 mechanism is not suitable for use with blanks. BFAs used with recoil operated firearms typically replace the locked breech of a recoil operated firearm with a simple blowback system using a restricted barrel, similar to a gas operated BFA. Short recoil operated pistol

Pistol

When distinguished as a subset of handguns, a pistol is a handgun with a chamber that is integral with the barrel, as opposed to a revolver, wherein the chamber is separate from the barrel as a revolving cylinder. Typically, pistols have an effective range of about 100 feet.-History:The pistol...

s, the most common type used for self defense and by police, are typically converted with a simple barrel replacement; the replacement barrel will lack the locking lugs to lock the slide to the frame, and will be built with an adjustable restrictor to control the chamber pressure. On designs with tilting barrels (again, the majority of modern designs are like this) there may also be a provision for tilting the barrel back, simulating the unlocking of the slide — this is visible in US Patent

United States patent law

United States patent law was established "to promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries;" as provided by the United States Constitution. Congress implemented these...

 5,585,589 listed below.

One notable exception to the design of BFAs for recoil operated firearms is machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

s based on short recoil designs, such as the German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 MG42

MG42

The MG 42 is a 7.9mm universal machine gun that was developed in Nazi Germany and entered service with the Wehrmacht in 1942...

 light machine gun

Light machine gun

A light machine gun is a machine gun designed to be employed by an individual soldier, with or without an assistant, as an infantry support weapon. Light machine guns are often used as squad automatic weapons.-Characteristics:...

 and its descendants. These designs use a muzzle booster

Muzzle booster

A muzzle booster or recoil booster is a device affixed to the muzzle of a firearm, intended to harness the energy of the escaping propellant to augment the force of recoil on portions of the firearm. Muzzle boosters are usually used to improve the reliability of a recoil operated firearm...

 to add energy to the recoiling parts, and muzzle brakes for these designs simply replace the muzzle booster with one that provides far more boost with blank cartridges. The M2 heavy machine gun

Heavy machine gun

The heavy machine gun or HMG is a larger class of machine gun generally recognized to refer to two separate stages of machine gun development. The term was originally used to refer to the early generation of machine guns which came into widespread use in World War I...

, while it does not use a muzzle booster normally, can use a similar muzzle booster derived BFA.

External links

, Blank firing conversions for semi-automatic pistols

Semi-automatic self-loading pistol

A semi-automatic pistol is a type of handgun which uses a single chamber and barrel, with a mechanism powered by the previous shot to load a fresh cartridge into the chamber...