Many AR rifle owners choose to build their own rifles, which is facilitated by a huge variety of barrels and other components.
The custom built AR may have a barrel from 7.5" (which is classed as a pistol) to as long as 24" used in varmint rifles primarily, often with Wylde or Noveske chambering.
In November of that year, testing at Aberdeen Proving Ground showed the AR-15 failure rate had declined to 2.5/1,000, resulting in the AR-15 being approved for air force trials.
In the spring of 1962 Remington submitted the specifications of the .223 Remington to the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI).
Testing was done with a Remington 722 rifle with a 22" Apex barrel.
During a public demonstration the round successfully penetrated the US steel helmet as required, but testing showed chamber pressures to be excessively high.
The .223 Remington (.223 Rem) is a rifle cartridge.
It started as the .222 Special and was renamed .223 Remington.
The development of the cartridge which eventually became the .223 Remington was intrinsically linked to the development of a new lightweight combat rifle. Eugene Stoner of Arma Lite was invited to scale down the AR-10 (7.62 mm) design. Springfield Armory's Earle Harvey lengthened the .222 Remington cartridge case to meet the requirements. Concurrently with the SCHV project Springfield armory was developing a 7.62 mm rifle.Because of several different .222 caliber cartridges which were being developed for the SCHV project, the .222 Special was renamed .223 Remington.In May 1959 a report was produced stating that five to seven man squads armed with AR-15 rifles have a higher hit probability than 11 man squads armed with the M-14 rifle.Robert Hutton (technical editor of Guns and Ammo magazine) started development of a powder load to reach the 3,300 fps goal.He used Du Pont IMR4198, IMR3031 and an Olin powder to work up loads.A variety of .223 Remington cartridges and a .308 Winchester (right) for comparison.Bullets in .223 cartridges (left to right): Montana Gold 55 grain full metal jacket, Sierra 55 grain Spitzer boat tail, Nosler/Winchester 55 grain combined technology, Hornady 60 grain V-Max, Barnes 62 grain Tipped Triple-Shock X, Nosler 69 grain hollow point boat tail, Swift 75 grain Scirocco II.US AR builders tend to follow the same trend as the US military in building rifles with Picatinny rails that support many accessories.The external dimensional specifications of .223 Remington and 5.56 NATO brass cases are identical.Case capacities have been observed to vary by as much as 2.6 grains.Sierra provides separate loading sections for .223 Rem and 5.56 mm NATO and also recommends different loads for bolt action rifles as compared to semi-automatic rifles.