In firearms terminology, an action is the functional mechanism of a breech-loading firearm that handles the ammunition cartridges, or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all those are single-shot firearms with a closed off breech with the powder and projectile manually loaded from the muzzle. Instead, the muzzleloader ignition mechanism is referred to as the lock.
The Colt AR-15 is a lightweight, magazine-fed, gas-operated semi-automatic rifle. It is a semi-automatic version of the M16 rifle sold for the civilian and law enforcement markets in the United States. Colt's Manufacturing Company currently owns the AR-15 trademark, which is used exclusively for its line of semi-automatic AR-15 rifles.
The M4 carbine is a 5.56×45mm NATO, gas-operated, magazine-fed, carbine developed in the United States during the 1980s. It is a shortened version of the M16A2 assault rifle.
Remington Arms Company, LLC was an American manufacturer of firearms and ammunition, now broken into two companies, each bearing the Remington name. The firearms manufacturer is Remington Arms. The ammunition business is simply called Remington. The company which was broken up was called Remington Outdoor Company. The Marlin Firearms division of the Remington Outdoor Company was purchased by Sturm, Ruger & Co. in 2020.
The Heckler & Koch HK416 is a gas-operated assault rifle chambered for the 5.56×45mm NATO cartridge. It is designed and manufactured by the German company Heckler & Koch.
The Barrett REC7 is an American firearm manufactured as a selective-fire fully-automatic and semi-automatic rifle by Barrett Firearms. It is an M4 carbine utilizing a short-stroke gas piston system. REC7 is available in either 5.56×45mm NATO or 6.8mm Remington SPC. The REC7 is Barrett’s second AR-pattern rifle chambered for the 6.8mm Remington SPC cartridge, the first being the Barrett M468 rifle. The 6.8 SPC-chambered M468 rifle employed the same direct gas-impingement system as the M4.
The T65 is a rifle developed and manufactured by the Combined Logistics Command of the Republic of China Armed Forces in Taiwan. Originally patterned after the Armalite AR-18 that has a short-stroke gas system, the prototype unveiled in 1975 showed a rifle that is heavily influenced by the AR-15 family of rifles, albeit with modified iron sights, a reshaped stock, and redesigned handguards. The designated number '65' refers to the Year 65 of Republic of China (1976), the year the rifle's design was finalized. Upgraded versions were designated the Type 65K2 and Type 65K3.
The SG 550 is an assault rifle manufactured by Swiss Arms AG in Switzerland. "SG" is an abbreviation for Sturmgewehr. The rifle is based on the earlier 5.56×45mm NATO SIG SG 540.
A STANAG magazine or NATO magazine is a type of detachable firearm magazine proposed by NATO in October 1980. Shortly after NATO's acceptance of the 5.56×45mm NATO rifle cartridge, Draft Standardization Agreement (STANAG) 4179 was proposed in order to allow NATO members to easily share rifle ammunition and magazines down to the individual soldier level. The U.S. M16 rifle's magazine proportions were proposed for standardization. Many NATO members, but not all, subsequently developed or purchased rifles with the ability to accept this type of magazine. However, the standard was never ratified and remains a "Draft STANAG".
The SG 540 is a 5.56×45mm NATO assault rifle developed in the early 1970s by Schweizerische Industrie Gesellschaft of Neuhausen, Switzerland as a private venture primarily destined for export markets and as a potential replacement for the 7.5×55mm Swiss SG 510 automatic rifle known as the Stgw 57 in Swiss service.
The Smith & Wesson M&P15 is an AR-15 style semi-automatic rifle by gun manufacturer Smith & Wesson. Introduced in 2006, the firearm is designed for police and consumer markets.
The Adaptive Combat Rifle (ACR) is a modular assault rifle designed by Magpul Industries of Austin, Texas, and known initially as the Masada.
The Remington R4 is a firearms platform based on the AR-15/M16/M4/M4A1 series designed and manufactured by Remington Arms.
Lewis Machine and Tool Company (LMT) is an American armaments company founded by Karl Lewis in 1980. LMT manufactures complete weapon systems such as the M4 carbine and the M203 grenade launcher. LMT products are used by the military forces of the United Kingdom, New Zealand, Estonia and the United States.
The SIG Sauer SIG516 is a semi-automatic rifle manufactured by SIG Sauer. It is an AR-15 style rifle chambered in 5.56×45mm NATO. Introduced in 2010, the SIG516 was discontinued as of 2019. A variant chambered in 7.62x51mm NATO, the SIG716i, remains in production.
An AR-15-style rifle is any lightweight semi-automatic rifle based on the Colt AR-15 design. The original ArmaLite AR-15 is a scaled-down derivative of Eugene Stoner's ArmaLite AR-10 design. The then Fairchild Engine and Airplane Corporation division ArmaLite sold the patent and trademarks to Colt's Manufacturing Company in 1959. After most of Colt's patents for the Colt AR-15 expired in 1977, many firearm manufacturers began to produce copies of the Colt AR-15 under various names. While the patents are expired, Colt retained the trademark of the AR-15 and is the sole manufacturer able to label their firearms as AR-15. The "AR" in Colt AR-15 stands for "ArmaLite Rifle", not "assault rifle".
The SIG MPX is a gas-operated submachine gun designed and manufactured by SIG Sauer, and is primarily chambered in 9×19mm Parabellum cartridge. It is a gas-operated firearm featuring a closed, rotating bolt. These design features, rare in submachine guns, were chosen to enhance the safety of the user and to have a more reliable firearm. It was designed in 2013 and was released to the general public in 2015. It features the SIG Sauer short stroke push-rod gas system to reduce the recoil and improve the reliability of the weapon.
The SIG MCX is a family of firearms designed and manufactured by SIG Sauer, produced in both selective fire and semi-automatic only models, and features a short-stroke gas piston system, which is inherited from the earlier SIG MPX submachine gun. The MCX is available in rifle, carbine, short-barreled rifle, and pistol configurations. The rifle was further developed into the SIG MCX Spear, which was adopted in its .277 Fury chambering as the XM5 by the U.S. Army in 2022.
The Next Generation Squad Weapon (NGSW) program is a United States military program created in 2017 to replace the M4 carbine and M249 SAW light machine gun and the 7.62mm M240 machine gun, with a common system with 6.8mm cartridges; and to develop small arms fire control systems for the new weapons.
