A bolt or quarrel is a dart-like

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...

used by

crossbow A crossbow is a ranged weapon using an Elasticity (physics), elastic launching device consisting of a Bow and arrow, bow-like assembly called a ''prod'', mounted horizontally on a main frame called a ''tiller'', which is hand-held in a similar f ...

s. The word ''quarrel'' is from the

Old French Old French (, , ; ) was the language spoken in most of the northern half of France approximately between the late 8th [2-4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ...

''quarrel'' (> French ''carreau'') "square thing", specialized use as ''quarrel d'arcbaleste'' (> ''carreau d'arbalète'') "crossbow quarrel", referring to their typically square heads. Although their lengths vary, bolts are typically shorter and heavier than traditional arrows shot with longbows.

Parts of the bolt

Point

The point, also called the ''head'' or the ''tip'', is the pointed and weighted front end of the bolt, which is sharp and hard so that it can penetrate the target.

Shaft

The shaft is the main body of the bolt to which other parts of the bolt are attached. In modern times it is normally made of

carbon fibre Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers ( Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon comp ...

or aluminium alloy (or sometimes both aluminum and carbon fibre are used), and is very lightweight for its strength. Shafts come with varying degrees of

stiffness Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a ...

— referred to as the " spine" of the bolt. The more resistant to bending a bolt is, the more "spine" it is said to have, and a crossbow with higher draw weight ideally needs to be paired with a heavier bolt point and higher spine specifications. The weight of a shaft is usually in

grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached husk, hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and ...

s, and product descriptions may provide the total weight in grains, or in grains per inch (GPI), for which the total weight of shaft can be calculated by multiplying the GPI value with length of shaft in inches.

Fletching

Fletchings, also referred to as ''vanes'', are fins located at the rear end of the shaft just before the nock. The fletching is typically made from soft light materials such as

feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and an exa ...

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

or silicone rubber. They stabilize the trajectory of the bolt via three different means: resisting pitching and yawing of the shaft by acting like a stabilizer fin (fin-stabilization); reducing deviation from the longitudinal axis by creating a back-pulling center of pressure behind the bolt's

center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weight function, weighted relative position (vector), position of the d ...

( drag-stabilization); and in some particular cases, creating a

rotation Rotation or rotational/rotary motion is the circular movement of an object around a central line, known as an ''axis of rotation''. A plane figure can rotate in either a clockwise or counterclockwise sense around a perpendicular axis intersect ...

around the longitudinal axis (spin-stabilization) by having the fletchings mounted at a slight

angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a Airfoil#Airfoil terminology, reference line on a body (often the chord (aircraft), chord line of an airfoil) and the vector (geometry), vector representing the relat ...

. There is no rule or formula for determining the length of fletching needed — generally the longer the shaft is, the longer the fletching needs to be, and vice versa.

Nock

A nock is a small notched piece that is attached to the rear end of the shaft, for engaging and receiving the propulsive push from the

string String or strings may refer to: *String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects Arts, entertainment, and media Films * ''Strings'' (1991 film), a Canadian anim ...

during shooting. Nocks are made of either plastic or aluminum.

Size and weight

There is not any hard and fast rule of bolt sizing. Generally, the bolts are 15 to 22 inches long but the standard length is 20 inches. Experts recommend longer bolts but they have certain disadvantages as well. The weight of the bolt can have a serious effect on the range of the bolt. The bolt's total weight includes the bolt's weight, nock, insert, vanes, and broadhead or field point. Almost all bolt manufacturers will list how many grains each shaft weighs or how many grains are in each inch of the shaft. A more massive bolt, e.g. at least 400 grains, will have better downrange energy and offer better penetration but will travel more slowly and thus drop more due to gravity during its flight. A lighter bolt will fly quicker and give the shooter a longer range, but might not have the desired penetration.

References

{{Authority control Archery Arrow types Crossbows Projectiles