Stock (firearms)


A gunstock or often simply stock, the back portion of which is also known as a shoulder stock, a buttstock, or simply a butt, is a part of a long gun that provides structural support, to which the barrel, action, and firing mechanism are attached. The stock also provides a means for the shooter to firmly brace the gun and easily aim with stability by being held against the user's shoulder when shooting the gun, and helps to counter muzzle rise by transmitting recoil straight into the shooter's body.
The tiller of a crossbow is functionally the equivalent of the stock on a gun.

History and etymology

The term stock in reference to firearms dates to 1571 is derived from the Germanic word Stock, meaning tree trunk, referring to the wooden nature of the gunstock.
Early hand cannons used a simple stick fitted into a socket in the breech end to provide a handle. The modern gunstock shape began to evolve with the introduction of the arquebus, a matchlock with a longer barrel and an actual lock mechanism, unlike the hand-applied match of the hand cannon. Firing a hand cannon requires careful application of the match while simultaneously aiming; the use of a matchlock handles the application of the slow match, freeing up a hand for support. With both hands available to aim, the arquebus could be braced with the shoulder, giving rise to the basic gunstock shape that has survived for over 500 years. This greatly improved the accuracy of the arquebus, to a level that would not be surpassed until the advent of rifled barrels.
The stocks of muskets introduced during the European colonization of the Americas were repurposed as hand-to-hand war clubs by Native Americans and First Nations when fragile accessories were damaged or scarce ammunition exhausted. Techniques for gunstock hand weapons are being revived by martial arts such as Okichitaw.

Anatomy of a gunstock

A gunstock is broadly divided into two parts, with the boundary roughly at where the trigger is. The rear portion is the butt, and front portion is the fore-end. The fore-end affixes and supports the receiver, and relays the recoil impulse from the barrel via a recoil lug. The butt is braced against the shooter's shoulder for stability and also interacts with the trigger hand, and is further divided into the comb, heel, toe, and grip. The stock pictured above has a thumbhole style grip, which allows a more ergonomic vertical hold for the user's hand.
In some modern firearm designs, the lower receiver and handguard replace the fore-end stock, leaving only the butt portion as the recognizable "stock", even though they serve the same function as the traditional fore-end.

Styles and features of stocks

The most basic categorization of stock types is into one-piece and two-piece stocks. In a one-piece stock, the butt and fore-end are a continuous monolithic piece, such as that commonly found on conventional bolt-action rifles. Two-piece stocks use separate pieces for the butt and fore-end, such as that commonly found on break-action and lever-action firearms. Traditionally, two-piece stocks were easier to make, since finding a quality wood blank suitable for a long one-piece stock is harder than finding short blanks for a two-piece stock.
In one-piece rifle stocks, the butt also varies in styles between the "European" type, which has a drop at the heel to favor quick shooting using iron sights; and "American" type, which the heel remains horizontal from the grip to favor more precision-oriented shooting using telescopic sights. There are also in-between designs with a "halfway" heel drop where the front half of the buttstock stays leveled.
Collapsible or folding stocks are often seen on military carbines, SMG/PDWs, their civilian-derived versions and some machine pistols. A collapsible stock makes the weapon shorter and more compact for storage, carrying and concealment, and can be deployed just before shooting for better control. A butt hook, which is an attachment to the butt of the gun that is put under the shooter's arm to prevent the rifle from pivoting forward from the weight of the barrel is sometimes used in competitive rifle shooting. These stocks are also used on combat shotguns like the Franchi SPAS-12 to allow the stock to collapse when not in use.

Grip

The grip is at the front portion of the butt that connects with the fore-end, and is held by the shooter's trigger hand during firing. The back surface of butt front near the grip is called the tang. Many grips have roughened textures or even finger grooves engraved into the sides to increase the firmness of the shooter's hold. Some grips have a thumb rest carved near the tang to give a more ergonomic hold for the trigger finger.
The grip varies widely in styles. A straight grip stock proceeds smoothly from toe to the trigger, giving a nearly horizontal holding angle for the trigger hand, while a full pistol grip stock contains a separate stand-out grip piece, providing a nearly vertical angle for the trigger hand for maximal ergonomics, and is commonly found on modern military rifles such as the ubiquitous AK-47 and M16/M4 families of assault rifles. In between the two extremes, the semi-grip stock is perhaps the most common sporting rifle stock, with a steeper angle cut into the stock to provide a more diagonal angle for the trigger hand. Modern target-style stocks have generally moved towards a fuller, more vertical grip, though built into the stock rather than made as a separate piece. Anschütz grip stocks, for example, use a nearly vertical grip, and many thumbhole grip stocks are similar to pistol grips in shape.

Comb

The comb is another area of wide variation. Since the comb must support the shooter's cheek at a height that steadily aligns the aiming eye with the weapon's sights, higher sights such as telescopic sights require higher combs.
The simplest form is a straight comb, which is the default form seen in all traditional rifles with iron sights. The Monte Carlo comb is commonly found on stocks designed for use with scopes, and features an elevated comb to lift the cheek higher, while keeping the heel of the stock low. If the elevated comb is of a rounded dome shape, it is often called a hogback comb. A cheekpiece is a raised section protruding from the side of the stock, which provides a more conformed support for the shooter's cheek. There is some confusion between these terms, as the features are often combined, with the raised rollover cheekpiece extending across the top of the stock to form essentially an exaggeratedly wide and high Monte Carlo comb.
Some modern buttstocks have a movable comb piece called a cheek rest or cheek rise, which offers adjustable comb height that tailors to the shooter's ergonomic preference.

Fore-end

The fore-ends tend to vary both in thickness, from the splinter fore-ends common on British side-by-side shotguns to the wide, flat bottomed beavertail fore-ends found on benchrest shooting guns, and in length, from the short AK-47 style to the long Mannlicher stock that runs all the way to the muzzle. Most common on sporting firearms is the half-stock, which extends roughly half the length of the barrel.

Stock measurements

Stock measurements are important regarding target rifle stocks if competing in IBS or NBRSA registered matches. The target rifle stocks must meet certain dimensional and configuration criteria according to the class of competition engaged in. Stock dimensioning is especially important with shotguns, where the typical front-bead-only sight requires a consistent positioning of the shooter's eye over the center of the barrel for good accuracy. When having a stock custom built or bent to fit, there are a number of measurements that are important.
  • Sight line, a datum line along the line of visual aim, extending axially to all points necessary for shotgun stock reference measurements.
  • Length of pull, the length measured from the back end of the butt to the trigger. Many newer stock designs have an adjustable length of pull. Other relevant length measurements affected by the length of pull include length to sight and length to handstop.
  • Drop at heel, the distance from the sightline to the heel of the butt. Sometimes also called the height of the buttpad or buttplate height.
  • Drop at comb, the distance from the sightline to the comb. Sometimes also called the height of the cheek rest or cheekpiece height.
  • Cast is sometimes also called offset.
  • *Cast off, the distance from the center of the butt to the Sight line, to the right side as seen from the rear. Often used by those shooting from the right shoulder.
  • *Cast on, the distance from the center of the butt to the Sight line, to the left side as seen from the rear. Often used by those shooting from the left shoulder.
  • Pitch, the vertical angle of the butt of the stock, determined by a straight line from heel to toe, referenced perpendicular to the Sight line.
  • Cant, the angle of the butt of the stock, rotated around an axis parallel to the bore line, referenced to zero degrees if pointing vertical to the ground.
  • Bore line, A datum line concentric with the barrel bore and extending axially to all points necessary for rifle stock reference measurements.
  • Recoil arm, the vertical distance between the bore axis and the contact point of the stock against the shoulder where the recoil acts. If the recoil line corresponds to the bore line, the firearm can recoil straight backwards and minimize muzzle rise.
  • Corporal line, the bottom edge of the butt of the stock, or as determined by a straight line from grip to toe.
  • Corporal angle, the angle of the corporal line referenced to the bore line at the corporal intercept point.
  • Corporal intercept point, the point on the bore line forward of the bolt face where the corporal line intercepts the bore line.
  • Handguard rotation, only found on firearms where the handguard can be rotated.