The press of the trigger--if marksmanship was an animal, this would be the heart of the beast. It must come straight back, smoothly and uninterrupted if the shot is to break without pulling the muzzle and the sights off the mark. The index finger and the trigger constitute a critical interface between operator and machine. For a perfect shot, a trigger whose surface is properly configured to the task can be extremely important.
Length of Trigger Travel as Determinant
The optimum trigger format will depend largely on how far the finger has to pull it. A wide, serrated trigger has long been the choice of marksmen who shoot semiautomatic target guns or single shot pistols, which have very short trigger pulls. There is usually only a very light pressure to overcome, and the precise target shooter wants the exact instant of the shot to come by surprise. The wider trigger face better distributes the finger's pressure, creating the felt sensation of an even lighter pull. The serrations, in theory, prevent the finger from slipping and losing its perfectly consistent placement during this very brief rearward trigger travel.
Trigger pull becomes longer and heavier as you go to more combat-oriented guns and shooting techniques. Consider the double action revolver, fired with the long, heavy pull of true double action, as opposed to being thumb-cocked for a crisp, easy single action pull. In DA shooting, the trigger travels so much farther back, the finger is likely to change its orientation, moving slightly across the surface.
Revolver shooters learned early that the wide, grooved "target triggers" of match revolvers like the Colt Officer's Model or the Smith & Wesson K-38, designed for single action use on bullseye ranges, were less than optimal for double action work. If you were right-handed, your index finger would be placing most of its pressure on the right edge of the wide trigger as you began the pull, tugging the muzzle to the right. As the trigger came further back, the finger would find itself applying most of its pressure to the left side of the trigger, whipsawing the muzzle back to the left. These two deviations would not usually compensate for one another and the result tended to be wild hits.
Wheelgunners learned to narrow their triggers. At one time S&W promoted their "Ranger trigger," three quarters the width of the full...