Trigger Mechanism Design Rules

[popgun pete]

Pneumatic spearguns generally use a form of single piece trigger which is flattened out to sit inside the gun and is operated by an external trigger sitting outside the gun's air pressure chamber. A single piece trigger is a hooking mechanism and this diagram shows what is happening as the external trigger tips them over. Any tilt on the sear lever and the torques from the forces created by the inner barrel sliding piston being under high air pressure and operating around the sear lever pivot pin begin to change rotation direction and the gun shoots. With the sear lever in the latch position the torque holds the sear lever front end up keeping the piston hooked. Once the piston unhooks from the sear lever tooth it will zoom down the inner barrel pushing the spear out of the gun. You only want that to happen with a definite swing of the external trigger, not a slight touch, or none! Pre-tilted sear levers are asking for trouble as the gun may shoot without pulling the trigger, or possibly the slightest touch. If interconnected with a line release the danger is the gun may shoot before the line release disengages fully, snapping the shooting line or the line release lever clean off. Watch out!