The tranquilizer gun

The tranquilizer gun now used all over the world was invented by New Zealand Veterinary Surgeon Colin Murdoch from Timaru who patented the gun in 1959.

The problems he faced in designing the gun included being able to deliver a varied dose according to the animal’s size plus a controlled projectile speed according to distance and thickness of the animal’s skin. No matter how far away from the animal the needle needs to just stick into the skin without braking a bone.

The invention was waiting for an expert in gun making, animal physiology , ballistics, pharmaceuticals and anaesthesia.

Colin developed both pistols and rifles which had interchangeable barrels for different calibre syringe projectiles. Each gun has a twisting dial which controls the forward size of the pre-expansion chamber between the cartridge and the projectile. This can be set at thirty two positions. allowing to shoot into a cage a few feet away or an animal up to 150 metres distant.

The syringes are made of strong light polycarbonate plastic with a needle threaded into the front and a small shuttlecock like tail to give stability in flight and so great accuracy. On impact a special valve system inside the syringe pushed the dose into the animal.

At Colin’s first tests were on dog tucker rams in the Timaru district. When perfected he formed a company, Paxarms, which produced and exported the guns all over the world.