A blank-firing adapter or blank-firing attachment (BFA), sometimes called a blank adapter or blank attachment, is a device used in conjunction with
blank ammunition for safety reasons, functional reasons or a combination of them both. Blank firing adapters are required for allowing blank ammunition to cycle the bolts of most
semi-automatic and
automatic firearms. It can also be a safety feature designed to break up the (wooden or plastic) plugs replacing the bullet in military blanks (with the added benefit that a live round mistakenly fired will spend most of the energy smashing through the BFA reducing both the range and damage inflicted) as well as divert the hot gases from a blank discharge out to the sides, reducing the risk of injury to the target of an aimed shot.
Design
The design of the blank firing adapter depends on the intended use. Different designs are used for different
firearm actions 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
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, 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 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 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