The ArmaLite / Colt AR-15 is one of the most favored automatic rifle systems in the world today. The type is considerably enjoyed throughout the United States where its citizens enjoy certain firearm-related freedoms not seen in other developed nations. The AR-15 has proven to be a highly modular, accurate and easy-to-use and maintain system which has only furthered its reach the world over. Hundreds of thousands of examples are currently in circulation and the type has seen uninterrupted production since its inception in 1958.
The ArmaLite concern was founded in 1954 and became a developer of small arms systems, the company based out of its Illinois headquarters. One of its key people became famed gunsmith Eugene Stoner (1922-1997), who - in the eyes of many - could lay claim to his influence in the world of firearms comparable to the great John Browning himself. Stoner, who became chief engineer at ArmaLite in 1954, lent his considerable talents to the design of several promising though unfulfilled small arms productions. In 1955, Stoner developed the AR-10 rifle, a system chambering the 7.62x51mm NATO standard round, offering selective fire and being of relatively lightweight in its construction - highly suitable for use in a military environment. Seeing potential long-term revenue of the rifle in US military hands, ArmaLite entered their AR-10 design into competition to become the next US Army standard infantry rifle. However, the type was rejected in favor of the T44 prototype (a safer approach in the eyes of the US Army), eventually to become the M14 rifle -- an evolution of the World War 2-era M1 Garand.
Nevertheless, all was not lost for the future of the AR-10 for the US Army continued its interest in the AR-10 and called for some revisions to the basic design. One of the major changes was in the chambering of the smaller .223 Remington cartridge. The resulting rifle design was then designated as the "AR-15" which formally appeared in 1958. Amidst financial troubles, ArmaLite was forced to sell off its AR-10 and AR-15 designs to competing Colt and Stoner himself eventually left ArmaLite in 1961. The AR-15 was eventually adopted into the US Army inventory as the well-known "M16" while Colt also took the rifle to the civilian market as the "Colt AR-15" (a registered company trademark) and these were completed as semi-automatic rifles beginning sales in 1963.
Outwardly, the AR-15 shared much of the appearance of the highly recognized M16 infantry rifle of the US Army. The receiver (specifically made up of of a lower and upper section) included all of the major internal working components including the low-set magazine feed, angled pistol grip and trigger group. The trigger was curved forward and protected by a thin ring guard. The pistol grip and magazine well supported the trigger system at the rear and front respectively. The upper receiver component managed the ejection port and cocking mechanism -both set to the right-hand side of the weapon. An optional carrying handle was well-integrated into the design and set about the upper receiver. A forend covered the barrel assembly and protected the operator's hand from the hot barrel. The barrel protruded ahead of the forend and was capped by a baffled muzzle brake. An adjustable triangular-appearing forward sight adorned the weapon aft of the barrel but forward of the forend. There was also an adjustable rear sight for precise firing. At the rear of the receiver there was fitted a shoulder stock. The magazine feed accepted various-count magazines - straight or curved in nature. The design eventually accepted a myriad of barrel lengths as well, these to suit specific operator requirements, ranging from 6.5 inches to 24 inches. Construction of AR-15s was of aluminum and synthetics making for a manageable 5.5-to-8.5lb operating weight.
As mentioned, the AR-15 was originally chambered for the .223 Remington. The firing action was of direct impingement with a rotating-lock bolt system. Direct impingement implied a gas operation system which reconstituted the erupting gasses from a fired cartridge and directed this into the bolt carrier to cycle the firing action for the next available cartridge (if any remained). Stoner proved a large proponent of the direct impingement system regarding automatic firearms. The AR-15 was an air-cooled rifle system to which the operator risked overheating the barrel through much subsequent firing without a break. Listed rate-of-fire was approximately 800 rounds per minute on full-automatic (if available on the particular AR-15 model). Muzzle velocity was rated at 3,200 feet per second. Effective range was out to 550 yards on average and depending on firing conditions. The AR-15 cartridge adaptability had since grown to include the .45 ACP, 5.7x28mm, the 6.5mm Grendel, the 6.8mm Remington SPC and .50 Beowulf with proper barrels, chamber pressurization and applicable changes to suit particular cartridge function.
Over time, the AR-15 has become a highly modular weapons system capable of being outfitted with various accessories to suit operator taste. This includes forward vertical grips, optics, bipods and the like. Its design has made it a highly accurate firearm and many users enjoy its lightweight nature and resilient body construction. Despite the AR-15's external likeness to the military-minded M16, the M16 makes use of semi-automatic fire, three-round burst capability and a full-automatic fire mode as well as the 5.56mm NATO standard cartridge through STANAG-type magazines. As such, the internal hammer and trigger systems are unique to each respective form and internal components of the AR-15 and M16 are not interchangeable for rather obvious reasons - one being to limit the ease of adapting the AR-15 to full-automatic fire in the civilian market.
The AR-15 has been further evolved to become the M4 Carbine, the CAR-15, the SR-47, the C7, the T65 and the Bushmaster C4. The M4 Carbine is a shortened version of the M16 assault rifle, intended for close-quarters battle (CQB) and has seen extensive service in the ongoing conflicts in Afghanistan and Iraq following the events of September 11th. The M4 appeared in US military service beginning in 1994. The CAR-15 is of similar form and function and appeared in 1968 and includes the shorter 11.5-inch barreled Colt Commando series. The SR-47 was a proposed assault rifle design put forward by the Knight Armament Company for possible acceptance by US SOCOM. It was never formally accepted into service nor serial production. The C7 became the standard Canadian Army service rifle in 1984 and was based on the M16A2 assault rifle model with changes to suit Canadian requirements. The T65 became a locally-produced Taiwanese version of the M16, beginning service in 1976. The Bushmaster M4 Carbine was based highly on the AR-15 and eventually went on to stock the inventories of some 60 countries worldwide in civilian, police and military forms.
Direct AR-15 variants are numerous and include the experimental XM16E1, the whole M16 family line, the CAR-15 family (carbine, heavy assault rifle and submachine gun types), the experimental XM177 series, the experimental XM4 Carbine and the aforementioned M4 Carbine line. Various civilian and specialized government models have also existed to date making the AR-15 one of the most successful rifle designs of its time.
The first widely-accepted AR-15 sales were made to Malaysia who acquired the type in number in late 1959. From there, Colt managed to secure more sales (including the lucrative U.S. military M16 contract) which solidified the AR-15 legacy in firearms lore. The system has also proven quote popular in its many forms and guises on the civilian market (where legally available) and has been featured in hunting outings and competitive shooting displays. Police and security forces also took to ownership of the type.
Over time, the AR-15 system - in one form or another - has been produced by a myriad of companies beyond the standard ArmaLite brand. These include American Spirit Arms, Bushmaster Firearms International, C3 Defense, Charles Daily Firearms, Colt, Daniel Defense, DPMS Panther Arms, High Standard Mfg Co, Les Baer, Lewis Machine and Tool Company, LWRC International, Olympic Arms, Remington, Rock River Arms, Sabre Defense, Smith & Wesson, Stag Arms, Ruger, Ruger and Company and Wilson Combat. As Colt maintains the "AR-15" trademark, other manufacturers of the rifle apply their own company model designations to their respective end products.
The "AR-15" designation simply comes from the abbreviated "ArmaLite" name, the "15" being nothing more than the company-assigned model number.