Sling (firearms)

In the context of firearms, a sling is a type of strap or harness designed to allow a shooter to conveniently carry a firearm (usually a long gun such as a rifle, carbine, shotgun, or submachine gun) on their body, and/or to aid in greater hit probability by allowing the firearm to be better braced and stabilized during aiming. Various types of slings offer their own advantages and disadvantages, and can generally be divided into several categories.
Mounting standards.
There are several mounting standards for attaching a sling to a rifle, of which some well known are sling swivel studs, QD/ Flush Cup or snap hooks (i.e. HK-type snap hook or Magpul Paraclip).
Sling mounts also come in different widths for different webbings. The webbing on American slings are typically 1, 1 or 1 inch (25.4, 31.75 or 38.1 mm) wide, while European slings typically are wide.
Sling swivel stud.
A "sling swivel stud", sometimes called an "Uncle Mike type swivel", is one type of sling mounting interface. Sling swivels can be mounted to a long gun in various ways, for instance with wood or machine screws attached to the stock, a barrel band, or by using adapters to other mounting standards such as Picatinny or M-LOK.
Sling swivel studs can vary in dimensions. The widest round part of the stud typically measures around 8.9 mm (0.350 inches), the spacing between the flats measure around 7.6 mm (0.3 inches) and the hole for mounting a sling adapter measures around 3.7 mm (0.145 inches).
Quick detach sling mount.
"Quick detach sling mounts" (QD), also called "flush cup sling mounts", is another type of sling mounting interface. "QD sling swivel" usually refers to the part attached to the sling, while "flush cup" refer to the corresponding socket on the firearm.
The system consists of a push button swivel attached to the sling (approximate diameter 9.4 mm, a little under inches) which is placed into a mounting socket on the firearm (approximate diameter 9.6 mm, a little over inches). The swivel is kept in place by a four ball detents connected to the push button, which presses against the walls of the socket. The sling swivel can quickly be taken on and off by pushing the QD button, which retracts the ball detents. The flush cup sockets can be either rotating or non rotating.
Flush cups can be mounted to a long gun in various ways, for instance by drilling a hole in the stock and screwing in flush cup socket, or by using an adapter to other mounting standards such as Picatinny or M-LOK.
As a shooting aid.
A variation of the single point sling is used in precision target rifle shooting from the prone position. The sling is not intended as a carrying aid, but is used to steady the rifle. For a right-handed shooter, the sling attaches to the top of the left arm, and clips onto the forend of the rifle. The left arm is wrapped under the sling. The sling with upper and lower arm form three sides of a triangle that provide a steady support for the rifle.
Carrying harness.
A carrying harness usually refers to a type of sling made primarily for carrying the rifle, and not doubling as a shooting support. For example in biathlon, the carrying harness is often a separate item from the shooting sling, with both being attached to the biathlon rifle. The carrying harness is designed to let the biathlete carry the rifle with minimal hindrance, and in such a way increase performance in the ski track. Special carrying harnesses have also been designed for anti-tank rifles, since such rifles often are too heavy for carrying with a normal rifle sling.