Brief History

The AR-15 Rifle was designed as the military M-16 in the 1960’s to be used in U.S. military trials as a replacement for the legacy the M-14. The company that designed the AR-15 was called Fairchild Aircraft and Engine Corporation.    The division, in which it was engineered was called Aramalite and headed by chief engineer Eugene Stoner.  It was initially designed around a .222 Remington cartridge, which was later upgraded to a .223 Remington cartridge at the request of the US military.  The AR-15 was also designed to propel a 55-grain bullet at about 3,000 feet per second.  The objective was that for the same weight, a solder could carry more ammunition in the AR-15 than the older M-14 rifle.

The US Airforce was the first to adopt the AR-15, after lengthy evaluation and revisions.  The army did not select the rifle, at the time, for a variety of political reasons.   This changed as the US became more involved in the Vietnam war.  At some point, Secretary of Defense James McNamara manage to cut through some political red tape, and the AR-15 was selected for standard issue to troops deployed to Viet Nam.  The army gave it a military designation of a M16, which now is used to distinguish the military version, versus the civilian version, or the AR-15.

After lengthy evaluation and revisions, the AR-15 rifle was only adopted by the U.S. Air Force for use by its base security personnel. For a variety of political reasons, the Army did not select the rifle. However, as America became involved in the Vietnam War, Secretary of Defense James McNamara cut through the Army Ordnance Department’s red tape and selected the AR-15 for issuance to troops. The Army gave it the military designation of “M-16”.

During its initial use during the war, the rifle earned a reputation for jamming and other stoppages.  This was due to several reasons:

  • Soldiers had not been trained on proper weapons maintenance.
  • Cleaning kits were generally not available in the field.
  • Poorly quality Remington .223 ammunition, which caused fouling.

In time, the army recognized the flaws and troops were provided higher quality ammunition, cleaning kits and training on proper maintenance.

Equipment Characteristics, Capabilities, and Features

The SIG Sauer AR-15 can be consider the best AR-15 that is commercially available due to it’s high quality European engineering.  The most popular model is the SIG M400, which is an enhanced AR-15 rifle.  It is lightweight, air cooled and gas operated and perfect for both offensive and defensive situations.   It is a magazine-fed rifle that is commercially available with a semi-automatic fire.  This can be modified to automatic using after market kits and increase your capability to engage targets while in the field role.  The  receivers are made of light-weight aluminum alloys; however, the safety, durability, and function of the rifles are in no way reduced. The portability and logistical values are greatly increased, particularly when air transport is used.

SIG M400 rifle or enhanced SIG Sauer AR-15

The SIG M400 is a direct impingment rifle featuring a rotary bolt mechanism, which is commercially available in a semi-automatic version, and upgrade-able to a full automatic firing operation.  To be clear – semi-automatic means that one round is fired, each time the trigger is pulled, until the magazine is emptied of ammunition.


sig sauer ar15

Sig Sauer AR-15

The bolt locking action is one of the mechanical features of the weapon. The bolt and barrel extension contains locking lugs which engage and lock the bolt firmly in the barrel extension. The initial force of the explosion of the cartridge propellant is absorbed by the barrel, barrel extension, and bolt.  The trigger guard is easily adaptable to winter operations. A spring-loaded retaining pin is depressed to allow ready access to the trigger when wearing arctic mittens. The ejection port cover prevents dirt or sand from getting into the ejection port, The cover must be closed during periods when firing is not anticipated. It opens automatically by the forward or rearward movement of the bolt carrier.

Location and High-Level Description Of Major Components

  • A) AR upper assembly –  The charging handle is what loads the weapon.
  • B)  Bolt carrier assembly – This sends to bolt to the chamber and fires the weapon. It contains the firing pin, extractor, bolt, ejector, and cam pin.
  • C) Upper Receiver. The rifle barrel assembly is air-cooled, contains flash suppressor and front sight assembly, and holds the two hand guards and the sling swivel. Upper receiver contains rear sight, ejection port and cover, and a housing for the bolt carrier and bolt assembly. The upper assembly also contains the hand guard which protects the barrel and the gas system from damage.  This also protects your hands from heat.
  • D) AR lower assembly – The lower receiver contains the trigger assembly, sear hammer assembly, selector lever, rifle grip, bolt catch, and butt-stock assembly. The AR butt-stock assembly houses the action spring, buffer assembly, and extension assembly.
  • E) AR magazine. 30 round cartridge capacity.
  • (F) Arm sling. The small arms sling is adjustable and provides a means to carry the weapon
sig sauer ar15 components

Component Location and Descriptions

Upper Assembly and Barrel

The barrel is mechanically attached to the receiver with the barrel nut and extension.  The flash suppressor, if needed, can be screwed onto the muzzle end.  The front sight housing, which is mounted on the barrel, contains the gas port and front sight.  The upper receiver can be used to attached an M1913 accessory rail so that you can attach a wide variety of different gadgets such as sights or optics.


Integrated Barrell Receiver Gas System

Integrated Barrell Receiver Gas System

Bolt Carrier Assembly

The bolt carrier assembly controls locking and unlocking via the camp pin.  The bolt carrier includes a carrier key that transfers gas from the gas tube to the belt carrier assembly.  The bolt carrier cocks the hammer.

Bolt Carrier System

Bolt Carrier System

Bolt Carrier

The bolt contains the firing pin with the extractor and ejector.  It includes the locking lugs that lock the bolt into the barrel extension.  The cam pin passes into the bolt, which provides locking and unlocking.  This is retained in the bolt by the firing pin.

bolt carrier

Bolt Carrier


Lower Assembly and Stock

The lower receiver assembly consists of the magazine well and release, the sling attachment point, the bolt catch lever, the fire control mechanism (or trigger) and the butt stock.

Lower Assembly Butt Stock

Lower Assembly and Butt Stock

The telescoping butt stock is adjustable and varies from model to model.  It can be adjusted to accommodate the size of the operator, or for storage.  Adjustment is as simple as pressing the release latch, and then pushing or pulling the stock to the desired position.

You can also remove the butt stock, by depressing the lever and sliding the stock to the full extension.   Once at end, pull the release latch and slide down the stock from the receiver.  You can re-install the stock by gently sliding it back on the receiver extension.

Included in the lower assembly is an extremely important safety feature – ie.  the safety:

Manual Safety Up Close

Manual Safety Up Close


It should be pretty obvious on how to operate this.  The safety should always be on unless you are in an appropriate setting and actually firing the gun.  The switch es exact and the safety is only “ON” when it is fulled turned to “ON.”  Also keep in mind – the only truly safe rifle, when not in use, is one that has an empty chamber and the magazine is not attached.

Trigger Operation

The SIG Sauer AR-15 features a trigger guard for safety.  It can be released temporarily if shooting with gloves, but should always be in place for safety purposes.  You can lower the guard by depressing the spring loaded retainer as shown below.  Be absolutely careful when operating any of these features.  For example, inserting a gloved finger, could discharge the weapon!

AR 15 Trigger Operation

AR 15 Trigger Operation

Impact of Legislation to Design and Capabilities

In 1994, the Clinton Administration made a number of features illegal on the civilian AR-15 version.  As a result, you typically have a “Pre-ban” or a “Post-ban” version.  You can use the gun serial number to understand whether it is a Pre-Ban or Post-Ban gun.  Post-Ban AR-15 cannot have more than two of the following features:

  • Detachable magazine
  • Pistol grip
  • Threaded barrel or flash hider
  • Collapsible stock
  • Bayonet Lug
  • Grenade launcher
detachable magazine

Detachable Magazine

Pistol Grip

Pistol Grip


Given this constraint, 99% of the Post-Ban AR-15 rifles maintain both the detachable magazine and pistol grip feature.  Some say, the legislation passed in 1994 which puts limits on our second amendment rights, actually improved the accuracy and weight of the rifle.

AR-15 Basic Training Video

4 Comments on “AR-15

    • Thank you sir! I know have full-time editor and will try to have fresh-content up regarding guns and personal freedoms. Thanks for your support!

  1. Thank you for the history lesson. I am shopping for the AR 15. I like the sigsauerar, but I also like the M&P. Also the Colt. I am from California many restrictions.

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