| Term | Definition | Category |
| Safety | Device that blocks the firing operation of a firearm. | |
| Scope | A telescopic sight, commonly called a scope, is an optical device used to give additional accuracy using a point of aim for firearms, airguns and crossbows. | |
| Semi Automatic | A type of firearm which, utilizing some of the recoil or some of the expanding-gas energy from the firing cartridge, cycles the action to eject the spent shell, to chamber a fresh one from a magazine and to cock the mainspring, placing the gun in position for another shot with nothing more needing to be done than to provide another pull on the trigger. | |
| Shotgun | A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug. Shotguns come in a wide variety of sizes, ranging from 5.5 mm (.22 inch) bore up to 5 cm (2 inch) bore, and in a range of firearm operating mechanisms, including breech loading, single-barreled, double or combination gun, pump-action, bolt-, and lever-action, semi-automatic, and even fully-automatic variants. | |
| Sight | A sight is an optical device used to assist aim by guiding the eye and aligning it with a weapon or other item to be pointed. Various forms of sights exist, such as iron sights, laser sights, reflex sights, peep sights, and telescopic sights. | |
| Single Action (SA) | An action type, typical on handguns, where the hammer must be cocked manually prior to each shot (if it be a revolver) or prior to the first shot with an already loaded chamber and de-cocked hammer (if it be a semi-automatic). | |
| Single Set Trigger | A single trigger, operating at a normal 4 - 6lb pull, which when pushed forward converts to a hair trigger. | |
| Single Shot | A firearm into which each shot must be manually loaded before it can be fired. | |
| Skeet | Competitive shotgun shooting at 'clay pigeons' thrown from two different locations. | |
| Sling (Sling Swivels) | Special metal posts are screwed into the stock near the butt and on the fore-end. Between these a sling is attached using sling swivels to be used for carrying a rifle over the shoulder. | |
| Slug | A single projectile designed to be fired from a shotgun. | |
| Slug Gun | A shotgun specially designed for shooting slugs, usually equipped with rifle sights. | |
| Soft Point | A bullet that has an exposed lead tip. | |
| Stock | A stock, also known as a buttstock or shoulder stock, is a part of a rifle or other firearm, to which the barrel and firing mechanism are attached, that is held against one's shoulder when firing the gun. The stock provides a means for the shooter to firmly support the device and easily aim it. | |
| Striker | A spring-driven firing pin. | |