STOCK (FIREARM)

A 'stock' or 'buttstock' or 'shoulder stock' is present in many firearms and some crossbows, and performs three functions - to facilitate easy and steady holding and aiming of the weapon prior to and during firing (which may be further assisted by a sling or a forward-mounted monopod, bipod or tripod); to transmit the recoil from the fired weapon into the shooter's shoulder, or as a weapon in itself as a club.
The term 'stock' is derived from the word stick, and 'butt' indicates the lower or thicker end of a piece of wood. Early weapons used sticks to support the barrel only, and later the buttstock was added to balance the weapon and steady the firer's aim when hand-held aiming was required. Foot-soldiers would thump the butts of their early muskets on the ground to assist in the loading process.
If a weapon is not fired from the shoulder (either because it is mounted on a tripod or a military vehicle, or held in the hands like a pistol), a shoulder stock is not appropriate. When a weapon is designed to switch between the role of portable and vehicle-mounted weapon, a detachable stock is often provided.
Similarly, in the case of many submachine guns and assault rifles (such as the pictured SIG 550, as well as some higher caliber target or sniper rifles (such as the Accuracy International AWP or Sako TRG) a collapsible or folding stock is provided so that the weapon can be conveniently fired from the shoulder, the hands, or the hip, as appropriate. When a weapon's working parts are housed in the stock, as for any bullpup design of assault rifle, they are positioned in the rear portion of the weapon.
Traditionally, stocks are from wood, generally a durable hardwood such as walnut. Collapsible stocks tend to be made from steel or alloy tubing, while modern composite stocks are generally fibre-reinforced plastic with a core of syntactic foam.