Captive bolt pistol

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A captive bolt pistol (stunner) is a device used for stunning animals prior to slaughter. The stunning is essential to prevent the pain and suffering of the animal while sticking (bleeding). The principle behind captive bolt stunning is to poleaxe the animal by the forceful strike on the forehead using a bolt which may or may not destroy the brain. The bolt is a rod made of some non-rusting alloys. It is held in position inside the barrel of the pistol or stunner by means of rubber washers. The bolt is not usually visible in a stunner in good condition. The bolt is propelled forwards by the discharge of a cartridge, which is detonated by a trigger. After striking on the forehead of the animal, the bolt recoils back into the barrel.

The captive bolt pistols are of two types, penetrating and non-penetrating.

In penetrating type, the stunner uses a pointed bolt which is propelled by a cartridge or pressurized air. The bolt penetrates the forehead of the animal and destroys the cerebrum and part of the cerebellum. Due to concussion, destruction of vital centres of brain and a reduction in intra-cranial pressure, the animal loses its consciousness and ability to feel pain. After striking, the bolt recoils back into the barrel.

In the non-penetrating type, the bolt used is blunt with a mushroom-shaped tip. The bolt strikes the forehead with great force and recoils back. This concussion is responsible for the unconsciousness of the animal. Such bolts prevent massive injury to the brain and make it suitable for human consumption.

The cartridges typically use 2 to 3 grains (130 to 190 mg) of gun powder, but can use up to 7 grains (450 mg) in the case of large animals such as bulls. The velocity of the bolt is usually 55 m/s in the case of small animals and 75 m/s in the case of large animals. There is another type of stunner called a free bullet stunner, which is used for the euthanasia of horses. There are certain specific stunning sites for various animals :

• BULL AND COW: The stunning site is at or below the point of intersection of two imaginary lines drawn from the base of the horn to the inner canthus of the eye.
• PIGS: The stunning site is on the forehead at a point 25 mm below the eyes. The stunner should be directed towards the gullet.
• SHEEP & GOATS: The stunning site is below the ridge which runs under the base of the horn. The direction of shot is towards the gullet.

For all polled animals, the site is at the centre of forehead, the shot being directed towards the gullet.