HISTORY

The AR-15 is based on the 7.62mm AR-10, designed by Eugene Stoner of the Fairchild ArmaLite corporation. The AR-15 was developed as a lighter, 5.56mm version of the AR-10. The "AR" in AR-15 comes from the ArmaLite name, not "assault rifle" as is commonly believed; ArmaLite's AR-1, AR-5, and some subsequent models were bolt action rifles, and there are shotguns and pistols whose model numbers also include the "AR" prefix. ArmaLite sold its rights to the AR-10 and AR-15 to Colt in 1959. Colt marketed the AR-15 rifle to various military services around the world, including the U.S. Air Force, Army, and Marine Corps. The AR-15 was eventually adopted by the United States military under the designation M16. However, Colt continued to use the AR-15 trademark for its semi-automatic variants (AR-15, AR-15A2) marketed to civilian and law-enforcement customers. The original AR-15 was a very lightweight weapon, weighing less than 6 pounds with empty magazine, though later heavy-barrel versions of the civilian AR-15 can weigh upwards of 8.5 lbs.

Today the civilian-model AR-15 and its variations are manufactured by many companies and have captured the affection of sport shooters and police forces around the world due to their low cost, accuracy, and modularity. (Please refer to the M16 for a more complete history of the development and evolution of the AR-15 and derivatives.)

The trademark "AR15" or "AR-15" is registered to Colt Industries, which maintains that the term should only be used to refer to their products. Other manufacturers make AR-15 clones marketed under separate designations, although colloquially, these are sometimes also referred to by the term "AR-15".

Some revolutionary or otherwise notable features of the AR-15:

• Aircraft grade aluminum receiver
• Modular design allows for a variety of accessories and makes repair easier
• Small caliber, accurate, high velocity round
• Synthetic stock and grips do not warp or splinter
• Front sight adjustable for elevation
• Rear sight adjustable for windage and elevation
• Wide array of optical devices available in addition to or as replacements of iron sights
• A direct impingement gas system

Semi-automatic and automatic variants of the AR-15 are effectively identical in appearance. Automatic variants have a rotating selective fire switch, allowing the operator to select between three modes: safe, semi-automatic, and either automatic or three round burst, depending on model. Civilian AR-15 models usually do not have three-round burst or automatic settings on the fire selector (e.g., Bushmaster Firearms. In semi-automatic only variants, the selector only rotates between safe and semi-automatic.

Type Automatic / Semi-automatic rifle / Service rifle

Place of origin U.S.

Service history

In service 1963 to present

Production history

Designer Eugene Stoner

Designed 1958

Specifications

Weight 2.27 kg - 3.9 kg (5.5 - 8.5 lb)

Barrel length 20 in (508 mm) standard

16 in (406 mm)

14.5 in (368 mm)

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Cartridge .223 Remington, 5.56 NATO

Action Direct impingement / Rotating bolt

Rate of fire 800 round/min

Muzzle velocity 975 m/s (3,200 ft/s)

Effective range 550 m (600 yd)

Feed system Various STANAG Magazines.

Sights Adjustable front and rear iron

	AR15 M16 HAND GUARD WEAVER STYLE RAIL 11 INCH AR 15 Handguard 11 inch picatinny rail mount easy to attach.
	AR15 M4 HAND GUARD 5.98 INCH WEAVER TYLE RAIL HANDGRIP COMBO AR15 M4 combo set offer 5.5" picatinny rail and 4.4" vertical handgrip.
	AR15 M4 HANDGUARD WEAVER STYLE SHORT RAIL 5.9 INCH AR15 M4 Handguard short rail mount with pre drilled hole-easy to install

Operation Machanism

The mechanism of operation for the rifle is known as direct gas impingement. Gas is tapped from the barrel as the bullet moves past a gas port located under the rifle's front sight base. The gas rushes into the port and down a gas tube located above the barrel. The gas tube runs from the front sight base into the AR-15's upper receiver. Here, the gas tube telescopes into a ?¡ãgas key?¡À which accepts the gas and funnels it into the bolt carrier. The movement of gas into the bolt carrier forces the bolt and carrier in opposite directions. As the bolt carrier moves towards the butt of the gun, the bolt begins to turn and unlock from the barrel extension. Once the bolt is fully unlocked it begins rearward movement along with the bolt carrier. The cam pin is responsible for the bolt's rotation as it follows a groove cut into the carrier that twists and forces the bolt to unlock. Once the bolt is unlocked, the bolt carrier and bolt continue to move towards the butt of the gun and the chambered casing is extracted and ejected out the side of the upper receiver.

A return spring located behind a buffer then pushes the bolt carrier back towards the chamber. A groove machined into the upper receiver traps the cam pin and prevents it and the bolt from rotating into a closed position. The bolt's locking lugs then push a fresh round out of the magazine, up the feed ramps and into the chamber. As the bolt's locking lugs move past the barrel extension, the cam pin is allowed to twist into a pocket milled into the upper receiver. This twisting action follows the groove cut into the carrier and forces the bolt to twist and ?¡ãlock?¡À into the barrel??s extension.

Variants

The AR15 rifle is available in a wide range of configurations from a number of manufacturers. These configurations range from short carbine-length models with features such as adjustable length stocks and optical sights, to heavy barrel models.

Aftermarket upper receivers that incorporate barrels of different weights and lengths, and handle different caliber ammunition, abound for this rifle. They are very easily installed, due to the rifle's modular design. These calibers include (in caliber size order):

• .22 Long Rifle
• .204 Ruger
• 5.56 ?? 45 mm NATO
• .223 Remington
• .243 WSM
• 6 x 45mm
• 6.5 Grendel (.264 cal)
• 6.8 SPC (.270 cal)
• .300 Whisper
• 7.62x39mm
• 9mm Parabellum
• .45 ACP
• .45 Bushmaster
• .458 SOCOM
• .50 AE
• .50 Beowulf
• .50 BMG

When installing a new complete upper receiver, particularly one designed to handle a different caliber of ammunition (i.e. other than .223 Remington or 5.56 x 45 mm NATO), some modification to the contents of the lower receiver may also be required, depending on the particular conversion. For example, a conversion to 9mm typically would involve the installation of a magwell block (to accommodate a typical 9mm magazine, such as Uzi or Colt SMG), replacing the .223 hammer with one designed for 9mm ammunition, and depending on your original stock, replacing the buffer, action spring and stock spacer for those designed for your new 9mm AR-15 configuration.

Earliest models had a 1:14 rate of twist, which was changed to 1:12 for original 55 grain (3.6 g) bullets. The 1:14 rate of twist showed to be unstable in colder temperatures. Most newer configurations use 1:9 and 1:7 twist rates. There is much controversy and speculation as to how differing twist rates affect ballistics and terminal performance with varying loads, but heavier projectiles tend to perform better with faster rifling rates. Additionally, the various non .223 / 5.56 calibers have their own particular twist rate.

Standard issue magazines are 20 or 30 round double column magazines, traditional box magazines also exist in 40 and 45 round capacities, and usable magazines have been constructed from a variety of materials including steel, aluminum, and high-impact plastics. Drum magazines with 90 and 100 round capacities also exist, such as Beta C-Mags. Low-capacity magazines, usually of a 5 or 10 round capacity, are available to comply with some areas' legal restrictions, hunting and because larger magazines can inhibit shooting from a benchrest.