The AR was a revolutionary design when it was first introduced. Originally designed by Eugene Stoner, chief engineer at ArmaLite (a division of Fairchild Engine and Airplane Corporation).
The AR-10 was developed as a lighter weight alternative to the other 7.62×51 service weapons being tested in the mid 1950’s (known as Project Salvo). The AR-10 was more than a pound lighter than the M14. It was a radical design for it’s time. It entered the competition late, and although it was passed over in favor of the M14, it left a good impression. Being that Fairchild Engine and Airplane Corporation dealt in the manufacturing and development of aircraft, many materials being used in that industry were incorporated into the AR design such as: plastics, aircraft grade aluminum (anodized), and other alloys. These materials offered strength but were much lighter than conventional materials used in firearms at the time.
The locking lugs on the bolt and the fact that the bolt carrier moved in line with the barrel helped to increase the accuracy compared to many other service rifles out there. Often dismissed by critics today for the gas-operated design, it’s advantages were that it saved on weight, it simplified the design (less parts to break) and helped to increase accuracy. It makes the BCG the piston so to speak. The drawback is that it dumps the carbon fouling into the chamber/breech.
However, proper lubing and modern improvements (and correct gunpowder) have been found to make this a non-issue. The direct impingement gas system also enhances accuracy. The plastic parts didn’t only save on weight but they also didn’t warp or splinter like wood. The receivers and magazines were made of aluminum, which is light. However, aluminum is also much weaker than steel.
In order to compensate for the weaker/lighter alloy, hard-coat anodizing the receiver(s) gave it a hard, durable outer shell. The AR was designed to be shooter friendly. If you’ve ever handled and/or fired an AR, you probably noticed that the safety and magazine release (among other things) were easy to find and manipulate. It works with the shooter. It’s like an extension of the user.
The AR-10 was redesigned shortly after its introduction in 1955 because the military wanted a smaller cartridge. They wanted a weapon in a smaller caliber that was easier to control in full-automatic fire and allowed troops to carry more ammunition.
Studies from past wars had taught them that most kills from small arms were at fairly close range, typically less than 300 meters. Studies had also taught us that the side that shoots the most rounds tends to get the most kills. The smaller round allowed for more ammo to be carried. The US military was not the only ones getting away from battle rifles and battle rifle cartridges. The Soviets as well as the British had looked extensively into developing a mid-range cartridge even smaller than the 7.62×51 NATO after WWII.
The Soviets got it in their SKS and AK-47 assault rifles chambered for 7.62×39 in the 1940’s.
The 7.62×51 NATO (top) vs. the Soviet 7.62×39 (bottom)
The British had tried to get the US military to consider their .280 round for NATO standardization years earlier, but we had instead forced the 7.62×51 on them. Imagine their dismay when we finally recognized the need for a smaller cartridge.
5.56 55gr M193 loaded in a 30 round magazine.
The AR-15 was designed to fit this exploration into a smaller caliber around 1958, which led to the development of the 5.56×45, commercially known as the .223Rem. ArmaLite sold the rights of the two designs to Colt in 1959.
The USAF and US Army began seriously looking at the AR-15. The USAF adopted it shortly thereafter and it was made the primary infantry weapon for all of the branches of the US military a few years later in 1967, despite resistance by some in the higher ranks of the Army and USMC. Dubbed, the “M16” (US Military designation), it replaced the M14 and M1 Carbine.
An M16/M4 is an AR15, but an AR15 is not necessarily an M16 or M4.
…look for part II of “AR-15 history” .