Length of pull (sometimes abbreviated as LOP) is the distance from the trigger to the part of a rifle or shotgun which fits against the shoulder of the shooter. Length of pull is an important ergonomic factor for ease of use; and optimum length of pull may vary with the size of the shooter, the thickness of chest clothing and body armor being worn,[1] and whether the shooter is firing from a standing, sitting, or prone position.[2]
Many rifles and shotguns are manufactured with a standard length of pull assumed to fit most shooters. This is often approximately 13.5 in (34 cm) for rifles[2] and about 0.8 in (2 cm) longer for shotguns.[1] Shooters with short arms may find the buttstock dragging along the underside of their arm as they attempt to raise the firearm into firing position. Shooters with broad shoulders or a long neck may experience face injuries from collision with the telescopic sight or thumb of the trigger hand as the firearm recoils. Modern firearms may be equipped with a telescoping stock or removable spacers to adjust the length of pull. Gunsmiths may adjust the length of pull of custom-built firearms or older firearms by cutting off a portion of the buttstock or adding a recoil pad to the buttstock.[3] Some sources[1][4] suggest a shooter's optimum length of pull will allow the butt of the firearm to exactly reach the inside of the elbow when the hand of that arm grips the unloaded firearm with a finger on the trigger. Other sources[5][6] suggest a more appropriate determination may be made using a non-firing "try-gun" resembling a firearm with an adjustable buttstock.[7] When a properly adjusted try-gun is held in a firing position, the shooter's nose should be about two finger-widths behind the thumb of the trigger hand.[8]