AR-15

AR-15
The AR-15 comes in many sizes and has many options, depending on the manufacturer. The part shown bottom center is the lower receiver, which under US law is the component legally considered the "firearm".
Type	Semi-automatic rifle / Service rifle
Place of origin	United States
Service history
In service	1958–present
Production history
Designer	Eugene Stoner
Designed	1957
Manufacturer	ArmaLite, Colt, Bushmaster, Rock River Arms, Stag Arms, DPMS Panther Arms, Olympic Arms, and others.
Specifications
Weight	2.27 kg–3.9 kg (5.5–8.5 lb)
Barrel length	24 in (610mm) 20 in (508 mm) standard 18 in (457 mm) 16 in (406 mm) 14.5 in (368 mm) 11.5 in (292 mm) 7 in (178 mm) 6.5 in (165mm)
Cartridge	.223 Remington, 5.56 NATO
Action	Direct impingement / Rotating bolt
Rate of fire	800 rounds/min (fully automatic versions only)[1][2][3]
Muzzle velocity	975 m/s (3,200 ft/s)[4]
Effective range	400–600 m (avg 547 yd)[5][6][7]
Feed system	Various STANAG magazines.
Sights	Adjustable front and rear iron sights

The AR-15 is a lightweight, 5.56 mm, air-cooled, gas-operated, magazine-fed semi-automatic rifle, with a rotating-lock bolt, actuated by direct impingement gas operation. It is manufactured with the extensive use of aluminum alloys and synthetic materials.

The AR-15 was first built by ArmaLite as a selective fire assault rifle for the United States armed forces. Because of financial problems, ArmaLite sold the AR-15 design to Colt. The select-fire AR-15 entered the US military system as the M16 rifle. Colt then marketed the Colt AR-15 as a semi-automatic version of the M16 rifle for civilian sales in 1963.^[8] The name "AR-15" is a Colt registered trademark, which refers only to the semi-automatic rifle.

History

The AR-15 is based on the 7.62 mm AR-10, designed by Eugene Stoner, Robert Fremont and James Sullivan of the Fairchild ArmaLite corporation.^[9] The AR-15 was developed as a lighter, 5.56 mm version of the AR-10. The "AR" in AR-15 comes from the ArmaLite name. ArmaLite's AR-1, AR-5, and some subsequent models were bolt action rifles, the AR-7 a semiautomatic survival rifle and there are shotguns and pistols whose model numbers include the "AR" prefix.^[9]

1973 Colt AR-15 SP1 rifle with 'slab side' upper receiver (no forward assist) and original Colt 20 round box magazine

ArmaLite sold its rights to the AR-10 and AR-15 to Colt in 1959. After a tour by Colt of the Far East, the first sale of AR-15s were made to Malaysia on 30 September 1959 with Colt's manufacture of their first 300 AR-15s in December 1959.^[10] Colt marketed the AR-15 rifle to various military services around the world, including the U.S. Navy, 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) which were 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.^[11]

Today the AR-15 and its variations are manufactured by many companies and have captured the affection of civilian shooters and police forces around the world due to their accuracy and modularity. (Please refer to the M16 for more history on 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 AR-15 manufacturers make AR-15 clones marketed under separate designations, although colloquially these are sometimes referred to by the term AR-15.

Some notable features of the AR-15 include:

• Aircraft grade forged 7075-T6 aluminium receiver is lightweight and highly corrosion-resistant
• Modular design allows for a variety of accessories and makes repair easier
• Straight-line stock design eliminates the fulcrum created by traditional bent stocks, reducing muzzle climb.
• Small caliber, accurate, high velocity round
• Synthetic stock and grips do not warp, swell 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
• Synthetic pistol grip (regulated in some states)

AR-15 sight picture

Semi-automatic AR-15s for sale to civilians are internally different from the full automatic M-16, although nearly identical in external appearance. The hammer and trigger mechanisms are of a different design. The bolt carrier and internal lower receiver of semi-automatic versions are milled differently, so that the firing mechanisms are not interchangeable. This was done to satisfy BATF requirements that civilian weapons may not be easily convertible to full-automatic. Despite this, through use of a "Drop In Auto Sear" or "lightning-link," conversion to full automatic is very straightforward (sometimes requiring slight modification to the bolt carrier).^[12][13] Such modifications, unless using registered and transferable parts made prior to May 19, 1986, are illegal. (The Firearm Owners Protection Act in 1986 has redefined a machinegun to include individual components where a semiautomatic firearm can be converted to full-automatic based on a 1981 BATF ruling on machinegun parts.)

Automatic variants have a three-position 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 do not have three-round burst or automatic settings on the fire selector. In semi-automatic only variants, the selector only rotates between safe and semi-automatic. Due to this, weapons modified to full automatic using a lightning-link are capable of full automatic fire only—unless a special full automatic fire select mechanism and modified selector-switch is substituted.^[12]

Operating mechanism

Diagram of an M16 rifle, firing

The mechanism of operation for the rifle is known as direct gas impingement. Gas is trapped from the barrel as the bullet moves past a gas port located above the rifle's front sight base. The gas rushes into the port and down a gas tube, located above the barrel, which runs from the front sight base into the AR-15's upper receiver. Here, the gas tube protrudes into a “gas key” (bolt carrier key) which accepts the gas and funnels it into the bolt carrier.

The bolt and bolt carrier together form a piston, which is caused to expand as the cavity in the bolt carrier fills with high pressure gas. The bolt is locked into the barrel extension, so this expansion forces the bolt carrier backward a short distance in line with the stock of the rifle to first unlock the bolt. As the bolt carrier moves toward the butt of the gun, the bolt cam pin, riding in a slot on the bolt carrier, forces the bolt to turn and unlock from the barrel extension. (The gas system only serves to unlock the bolt while the projectile has long exited the barrel). Once the bolt is fully unlocked it begins its rearward movement along with the bolt carrier. The bolt's rearward motion extracts the empty cartridge case from the chamber, and as soon as the neck of the case clears the barrel extension, the bolt's spring-loaded ejector forces it out the ejection port in the side of the upper receiver. The bolt is much heavier than the projectile, and along with the recoil-spring pressure inside the stock buffer-tube performs the cartridge ejection function and chambers the following cartridge.

20 and 30 round STANAG magazines compatible with the AR-15. Can be used in many other firearms such as the FN F2000, the M16, the FN SCAR, and more.

Behind the bolt carrier is a plastic or metal buffer which rests in line with a return spring that pushes the bolt carrier back toward 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 from the magazine which is guided by feed ramps 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 “lock” into the barrel’s unique extension.

Variants

See also: AR-15 variants

Colt AR-15 Sporter SP1 Carbine

The AR-15 rifle is available in a wide range of configurations from a large 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.

Due to the rifle's modular design, one upper receiver can quickly and easily be substituted for another. There are many aftermarket upper receivers that incorporate barrels of different weights, lengths and calibers. Some available calibers for the AR-15 platform are the .223 Remington/5.56x45mm, .45 ACP, 5.7x28mm, 6.5 mm Grendel, 6.8 mm Remington SPC,^[14] and .50 Beowulf.^[15] it is not recommended to chamber the 5.56x45 NATO into a rifle designated 223 Remington, due to the slighly increased chamber pressure in the 5.56mm cartridges, the two calibers are similar, but not identical.

Colt AR-15 A3 Tactical Carbine. Rifle is shown with a CQB Tactical Sling and a Colt 4x20 scope.

When installing a new complete upper receiver, particularly one designed to handle a different caliber of ammunition (i.e., other than .223 Remington or 5.56x45 mm NATO), some modification to the contents of the lower receiver may be required, depending on the particular conversion. For example, a conversion to 9 mm typically would involve the installation of a magazine well block (to accommodate a typical 9 mm magazine, such as Uzi or Colt SMG), replacing the .223 hammer with one designed for 9 mm ammunition, and depending on the original stock, replacing the buffer, action spring and stock spacer with those designed for the new 9 mm AR-15 configuration. The 9mm cartridge fires from an unlocked breech, or straight blow-back—rather than a locked breech, because the spring and bolt provide enough weight to allow this type of functioning. These guns do not utilize the direct gas impingement method of operation like the original.

Some AR-15's like the POF, LWRCI, H&K, Sturm Ruger, Sig Sauer, and Adams arms offerings replace the DGI (direct gas impingement) operating system with a short stroke/long stroke gas piston system. These guns usually have modified bolt carriers, gas keys, and gas blocks. When fired, DGI systems dump high pressure hot gas through the gas tube to the bolt carrier key and into the bolt carrier group. This can rapidly heat up the bolt carrier group and cause excessive fouling, one of the main complaints about the design. Gas piston operating systems alleviate these problems, but can be the cause of other issues such as bolt carrier tilt.

Upper and lower receivers machined from a solid billet (block) of aluminum as opposed to an aluminum forging are offered by some manufactures. These include Sun Devil manufacturing, LAR Grizzly manufacturing, POF-USA, and Black Rain. This is usually done for added strength.

Upper receivers utilizing a monolithic rail system that combine a railed hand guard and upper receiver into one uninterrupted piece are made by companies like Colt, POF-USA, and VLTOR. This is done to provide a continuous uninterrupted rail section that runs along the top of the gun from the weapons charging handle to the front sight/gas block. This rail section is used for the mounting of sights, laser aiming devices, night vision devices, and lighting systems.

A side charging upper receiver has been developed by LAR Grizzly. The charging handle can be had in a left side, right side, or ambidextrous configuration. Since the charging handle is attached to the bolt carrier making it a reciprocating design, it can be utilized as a forward assist device as well.

Early models had a 1:14 rate of twist for the original 55 grain (3.6 g) bullets. This was changed to 1:12 when it was found that 1:14 was insufficient to stabilize a bullet when fired in cold weather. Most recent rifles have a 1:9 or 1:7 twist rate. 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.^[16] Additionally, the various non .223 / 5.56 calibers have their own particular twist rate, such as 1:10, 1/11 and 1/12 for 6.8x43mm SPC, 1/10 7.62x39mm, and 1:12 for .308 Winchester.

A Colt AR-15 on display at the National Firearms Museum. This example is fitted with an early waffle-patterned 20-round magazine.

Standard issue magazines are 20 or 30 round staggered-column magazines, traditional box magazines 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 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.

Legal status

Australia

AR-15 rifles, like all semi-automatic rifles, are subject to strong restrictions of ownership in all states and territories in Australia. The only means of legally owning an AR-15/M16-type rifle in Australia today beyond law enforcement is to have a Category D Firearms License (e.g. a professional animal culler), to have a Firearms Collector's License and the firearm deactivated (with the barrel plugged up and the action welded shut), or converted to blank fire if one is a member of a military re-enactement organization.

The heavy restrictions on semi-automatic rifles was introduced in 1996 in response to the Port Arthur massacre – one of the firearms used in the attack was an AR-15. Before 1996, AR-15 rifles were legal to own in a number of Australian states and territories, namely Queensland and Tasmania.

Austria

In Austria, semi-automatic centerfire rifles have to be classified as sporting or hunting firearms in order to obtain civilian-legal status. After this classification, they are considered "category B" firearms, which means that holders of gun licenses may own them. These licenses are shall-issue items if the applicant specifies a valid reason (self-defense at home for example is considered valid by law in any case), passes a psychological test and attends a gun-basics course. Currently, only one centerfire AR-15 version, produced by German manufacturer "Oberland Arms" was given the B-classification. This Austrian version differs slightly from the original design in order to ensure that no military full-auto trigger, bolt and barrel may be installed. Additionally, bayonet lugs and flash hiders are prohibited on semi-automatic rifles while Muzzle brakes and compensators are legal. There is no minimum length for barrels, therefore even barrel lengths as short as 7.5" are possible.

Canada

The Government of Canada classifies the AR-15 (and its variants) as a restricted firearm. For anyone wanting to lawfully own an AR-15, they must first pass a "Canadian Non-Restricted Firearms Safety Test", and then a "Canadian Restricted Firearms Test". This allows the applicant to obtain a Possession and Acquisition License (PAL) valid for restricted firearms, subject to approval.^[17][18] With the introduction of strict gun control measures by former Prime Minister Jean Chrétien (Bill C-68), the AR-15 had originally been intended to be classified as a prohibited firearm, making it all but impossible to privately own one, however due to the presence of nationwide Service Rifle target shooting competitions, the AR-15 was granted a sporting exception.

As with all Restricted firearms (including most pistols, some shotguns, and some rifles) AR-15s are allowed to be fired only at certified firing ranges. In order to legally own and transport a Restricted firearm, the firearm must be registered with the Royal Canadian Mounted Police Canadian Firearms Program and must apply for an Authorization to Transport (or ATT) from the Chief Firearms Officer (CFO) for their province or territory. Additionally, the firearm must be unloaded, deactivated by a trigger or action lock, and be in a locked, opaque container during transport.^[19]

The issuance of ATTs varies considerably from province to province, and is generally reflective of a particular province's political and social levels of acceptance toward gun ownership. For example, in Alberta, where firearms ownership is widely accepted, generally a single ATT is promptly issued that allows citizens to transport firearms to border crossings, gunsmiths, and shooting ranges. Firearms transfers in provinces such as Quebec can take up to 3 months to process.^{[citation needed]}

Germany and Finland

In Germany and Finland, possession of semi-automatic rifles, including the AR-15, is legal, provided that the rifle's owner acquires a permit for owning one. A license is required for each individual firearm and there needs to be a specific reason for ownership such as participation in the shooting sports and hunting.

For German hunters, their semi-automatic firearm's magazine must be modified in such a way that its maximum capacity is only 2 rounds (excluding handguns), meaning that when hunting only 3 shots in total can be fired (as one additional round is loaded in the chamber) without reloading.

Sweden

The AR-15, like all other semi-automatic rifles, is legal for individuals who need one for competitive use (IPSC rifle or 3-gun matches). A valid competition license is required, and all weapons are registered with the police. There are no banned "assault weapon" features or parts. However, the AR-15 is not allowed for hunting use.

United Kingdom

As with all semi-automatic, centerfire rifles, AR-15s are classed as a Section 5 weapon (i.e. a person must provide an exceptional reason and gain permission from the Home Secretary, making ownership all but impossible for a private citizen.) However, AR-15s in a manually operated straight pull configuration or semi-automatic AR-15s that are chambered to fire a .22 rimfire cartridge are legal and can be held on a standard Section 1 Firearms Certificate. There are no restrictions on 'assault weapon features' in the UK, and no restrictions on magazine capacity. There are a number of UK manufacturers of "straight-pull" AR-15 variants. Southern Gun Company has tried to introduce a 9mm "self-ejecting" variant for gallery rifle shooting nicknamed the "Unicorn" but, despite numerous units being sold on the understanding that the rifle was a compliant Section 1 firearm, the rifles were seized and subjected to stringent testing by the UK licensing authority's Forensic Science Services (FSS). A small number of pre-production models were found to be non-compliant with section 1 status. However, later models were deemed Section 1 compliant and were returned to their owners.

United States

There are no federal restrictions on the ownership of AR-15 rifles in the United States. During the period 1994–2004 variants with certain features such as collapsible stocks, flash suppressors, and bayonet lugs were prohibited for sales to civilians by the Violent Crime Control and Law Enforcement Act of 1994, with the included Assault Weapons Ban. Included in this was a restriction on the pistol grip that protrudes beneath the stock, which was considered an accessory feature under the ban and was subject to restrictions. Some rifles were manufactured with a grip not described under the Ban installed in its place. Those AR-15s that were manufactured with those features were stamped, "Restricted Military/Government/Law Enforcement/Export Only" as well as the accompanying full capacity magazines. The restrictions only applied to guns manufactured after the ban took effect. It was legal to own, sell, or buy any gun built before 1994. Hundreds of thousands of pre-ban ARs were sold during the ban as well as new guns redesigned to be legal.

Since the expiration of the Federal AWB in September 2004,^[20] these features became legal in most states.^[21] Since the expiration of the ban the manufacture and sale of then-restricted rifles has resumed completely.

At least two states regulate possession of AR-15 rifles either by the restriction of certain features or outright bans of certain manufacturers' models. For example: the A3 tactical carbine pictured above is legal for sale and possession in the United States generally, but is illegal for sale in California.

Individual states

California

A California-legal AR-15 clone (FAR-15) with a 10 round magazine. Other notable features include pinned and welded muzzle brake, forward assist, "Bullet Button", collapsible stock & Aimpoint CompM4 (sight optic) mounted on the top rail.

The Roberti-Roos Assault Weapons Act of 1989 banned Colt AR-15 rifles by name. The 2000 Assault Weapons ban went further and banned AR-15s made by other manufacturer's by name such as Bushmaster, PWA, and Olympic Arms.^[22] After the expiration of the 2004 Federal Assault Weapin Ban there was a renewed interest in the AR-15 rifle and AR-15 styled rifles. It is estimated that some 400,000 California Legal AR-15s exist, with another 100,000 added each year. It should be noted that the term 'AR-15' is used loosely and broadly by the non-shooting public to refer to any rifle that represents a semi-automatic (one bullet shot per pull of the trigger) version of the military fully automatic (more than one round shot per pull of the trigger) version known as the M16. The M16 is a cosmetically similar military rifle to the AR-15 used worldwide by law enforcement and militaries and in the USA is strictly controlled by the National Firearms Act (NFA) enforced federally by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (BATFE or just 'ATF'). These following descriptions only adhere to the civilian legal semi-automatic versions in California which are under the purview and additional restrictions of California firearms law. Enforcement of California firearms laws are administrated by the California Department of Justice (DOJ) as they incur no federal triggers for firearms violations. There are three legal ways to own an AR-15/AR-15-type rifle in California:

1. Registered Assault Weapon: If the rifle was owned before Jan 1, 2000 and registered with the state, it is a Registered Assault Weapon (RAW) under CA law. No new registrations are permitted. RAW rifles can have features which are prohibited in unregistered rifles. This category is the ONLY one which allows for the use of the name 'AR-15' on the firearm itself, to whom, Colt Manufacturing Company owns the rights to. California has banned the AR-15 rifle specifically by name. Therefore, no other rifles are legal possess with such name without having first having been lawfully registered as an assault weapon with the California Department of Justice. Otherwise, one is in felony possession of an unregistered assault weapon for which no legal remedy exists if kept beyond the previously granted DOJ assault weapon registration grace period.
2. Fixed magazine Rifle: This style of rifle is made by combining an AR-15 upper receiver with an AR-15 lower receiver which has not been banned by specific name, and which has a fixed, non-detachable 10-round (maximum, anything above 10 is a felony) magazine. In such a configuration, otherwise prohibited features such as a telescoping stock, pistol grip, and flash hider may be present. While formerly prohibited under the now-expired federal assault weapon ban of 1994–2004, the presence of a bayonet lug is not prohibited by California state law and can be present on firearms without violation. However, the magazine cannot be detachable, so to load the rifle the shooter must either "top load" or use a tool to release the magazine lock (such as the tip of a bullet in 'Bullet Button' equipped rifles). To top-load, the shooter pulls the rear takedown pin, hinges the upper receiver on the front pivot pin, and loads the now exposed magazine. Alternatively, several 'magazine lock' devices are available which replace the magazine release button with an inset pin that requires the use of a special tool to release the magazine, thereby, disallowing a readily 'detachable magazine,' to be compliant with California state firearms law.
3. Featureless Rifle: If a rifle has none of the prohibited features (pistol grip, telescoping or folding stock, flash hider, grenade/flare launcher, forward pistol grip), the rifle may be used with legally owned large-capacity magazines that were in possession in the state of California PRIOR to January 1, 2000. Again, a bayonet lug is not a prohibited feature as noted above. There are several products available on the market to configure featureless rifles. To be compliant with the California state law, special grips are available which prevent the thumb and the web of the hand from going behind and below the top of the exposed trigger as would be the case with a pistol grip configuration. They are therefore not a prohibited wrap-around style grip. One specific example is where the California Department of Justice Bureau of Firearms attests by sworn testimony that the 'MonsterMan Grip' is not a pistol grip and therefore legal when used on a detachable magazine semiautomatic centerfire rifle with none of the features listed in CA PC 12276.1(a)(1)(A-F) as per sworn testimony of Frank Navarro, CA DOJ Bureau of Firearms Special Agent, in the case of People vs. Haack and Haack, California County of Tulare Superior Court, on November 3, 2010. Separate receiver extensions (buffer tubes) to contain the recoil spring and buffer assembly may be used in conjunction with special stocks without prohibited grips or stock adapters which attach to the pistol grip mount to be compliant with the state firearms laws.

Note: Most AR-15 manufacturers now make lower receivers which qualify as "Off-List" Lower (OLL) receivers which are legal to possess and use in the state of California. With regards to high capacity magazine devices, after January 1, 2000, it is illegal to offer for sale, import, manufacture, give, or lend (although it is legal to possess, use, buy, or receive) any detachable box magazine with a capacity exceeding 10 cartridges.^[23] The California State Attorney General's website indicates it is illegal to 'buy' in their FAQ; however, no such wording exists in the law. It is presumed that such wording was left out of the law specifically because those holding a California State Assault Weapons Permit, an armored car transport/carrier or security company and its personnel are able to 'buy' or purchase such high capacity magazines to carry out their duties even if not part of law enforcement entities. Individuals possessing such magazines at a lawful location such as a gun range may only allow use of their lawfully owned high-capacity magazines by another if they are in the immediate vicinity of the person using such items. All magazines acquired AFTER (and including) January 1, 2000 must be limited to 10 rounds or be in felony possession of an illegal high-capacity magazine. (Ref: http://ag.ca.gov/firearms/regagunfaqs.php)

Legal aspects of an AR-15

Under U.S. firearms laws, only the lower receiver of the AR-15 is considered a firearm and subject to purchasing restrictions. (This is not universally the case with rifles. On some other rifles, such as the FN FAL, Heckler & Koch 91, 93, (G-3, G-33), 94, MP-5 or SP-89 (plus clones), the lower receiver is the serial-numbered part, and thus the firearm.) The AR-15 upper receiver assembly is considered a part, and may be purchased and mail-ordered in most locations. This is a desirable feature for enthusiasts, who can purchase a number of upper receivers (often in different calibers and barrel lengths) and interchange them with the same lower receiver.

Adding a shoulder stock to an AR-15 with a barrel shorter than 16" would constitute constructing a Short-Barreled Rifle (SBR) under NFA rules – subjective to a $200 tax stamp. Constructing an AR-15 pistol using a lower receiver which had already been designated a rifle by the manufacturer (shipped out for distribution), not just described as such on an BATFE form 4473 when sold only as a receiver would constitute the construction of such a firearm, since the pistol was constructed from an existing rifle. The receiver, or serial-numbered part is still considered a firearm, but a receiver has unique status assigned by the Gun Control Act of 1968 as amended, and ATF regulations or rulings. ATF ruling 07-07-2009 illustrates a receiver's unique legal status even if the receiver can only be made into a rifle.^[24] Under the US v Thompson-Center Supreme Court ruling, an individual can possess parts for both the rifle and pistol so long as they are not assembled improperly.^[25]

If a lower receiver is designated and transferred as a pistol from an FFL dealer to a consumer purchaser, the owner can either assemble it as it was intended in pistol form or make a rifle out of it by installing a butt stock to lower pistol receiver and mate it with an upper receiver that possesses the federal minimum length of a 16" barrel (or short-barreled rifle if the barrel is less than 16" long and the appropriate tax stamp fee of $200 on a Form 1 PRIOR to construction). This change effectively creates legally a long gun which cannot be reverted back to a pistol configuration or the person would be in violation of having 'created' a short-barrel rifle. However, the saying "once a rifle always a rifle" comes into play as BATFE maintains that the finding in US vs. Thompson Contender, Inc. only applies to products of Thompson Contender and not to any other companies' products. With Thompson Contender products, the Supreme Court has ruled as above. No person/company to date has challenged the BATFE on this point with respect to other products under the same ruling, and as such, is untested legal grounds This has changed under atf ruling 2011–4 which states "A firearm, as defined by the National Firearms Act (NFA), 26 U.S.C. 5845(a)(3), is made when unassembled parts are placed in close proximity in such a way that they: (a) serve no useful purpose other than to make a rifle having a barrel or barrels of less than 16 inches in length; or (b) convert a complete weapon into such an NFA firearm. A firearm, as defined by 26 U.S.C. 5845(a)(3) and (a)(4), is not made when parts within a kit that were originally designed to be configured as both a pistol and a rifle are assembled or re-assembled in a configuration not regulated under the NFA (e.g., as a pistol, or a rifle with a barrel or barrels of 16 inches or more in length). A firearm, as defined by 26 U.S.C. 5845(a)(3) and (a)(4), is not made when a pistol is attached to a part or parts designed to convert the pistol into a rifle with a barrel or barrels of 16 inches or more in length, and the parts are later unassembled in a configuration not regulated under the NFA (e.g., as a pistol). A firearm, as defined by 26 U.S.C. 5845(a)(4), is made when a handgun or other weapon with an overall length of less than 26 inches, or a barrel or barrels of less than 16 inches in length, is assembled or produced from a weapon originally assembled or produced only as a rifle." Effective July 25,2011 Furthermore, adding a forward pistol grip to an AR-15 designated as a pistol constitutes manufacture or an AOW (any other weapon). Both of these actions require an approved "Form 1" and payment of a $200 tax for the short barrel conversion or a $5 tax for the AOW conversion PRIOR to the actual construction of the item. Current wait times for approval average 3–4 months during which time no modifications or construction may be done.

Malfunction

With the plethora of manufacturers of complete weapons and aftermarket barrels, there is a potential hazard associated with chamber specifications. Both civilian (SAAMI) specification .223 Remington and 5.56 mm NATO are available. Though both chambers typically accept both types of ammunition, the firing of military specification ammunition in civilian specification chambers can produce chamber pressures greater than the barrel is designed to handle. The most common result of firing military 5.56x45mm ammunition in a .223 Remington chamber is that the primer can be forced out of the case by chamber pressure, often resulting in the primer becoming lodged somewhere in the action of the rifle, and disassembly of the rifle is often necessary to remove the jammed primer.^[26] Military specification chambers typically have a more open throat area producing less pressure and can handle both types of ammunition.

A few AR-15 manufacturers incorporate the use of a hybrid chamber specification known as the Wylde chamber. Designed by and named after Bill Wylde, this chambering was designed to accurately shoot the military ball ammo of the day while still feeding reliably. Coincidentally, it shoots the longer 80 gr bullets commonly used in the sport of Highpower Rifle Competition very well and is one of the preferred chambers for that use. While the Wylde chamber allows for optimal seating depth of 80 grain bullets over .223 Remington and 5.56 NATO, it is capable of accepting both ammunition types. The Wylde chamber is used by a few manufacturers who sell "National Match" configuration AR-15 rifle, barrels, and upper receivers. The type of chamber, manufacturer, and rifling twist in inches is typically found stamped into the barrel in front of the front sight assembly. An additional point of concern in the design is the inertial firing pin. A lightweight firing pin rides in a channel inside the bolt unrestrained. When the bolt locks forward during loading, the firing pin typically rides forward and impacts the primer of the chambered round. In military specification ammunition and quality civilian ammunition, this is not normally enough to fire the round and only leaves a small "ding" on the primer. With more sensitive primers or improperly seated primers, this can cause a slamfire during loading.^[27]

Note: This situation is particularly poignant for owners of AR-15 rifles as a previous non-felon named David Olofson, an Army Reservist with 16 years in the US Army, loaned a 20-year-old AR-15 rifle to a prospective buyer for four months which was found to have fired multiple rounds on a single trigger pull at a gun range. After law enforcement intervention, he was charged with and found guilty in January 2008 of illegally transferring a machinegun when the AR-15 was found to have malfunctioned (defense contention)/purposely-modified (prosecution contention), was sentenced to thirty months in the Sandstone FCI federal prison in Wisconsin by a Federal Judge. The end result of this case finds that any firearm, including malfunction, which produces more than one discharge per pull of the trigger, is a machinegun, and thereby, its possessor or transferor, unless registered under provisions of the NFA is a felon.

AR-15 manufacturers

• American Spirit Arms
• ArmaLite
• Barrett Firearms Manufacturing
• Black Rain Ordinance
• Bushmaster Firearms International
• Bravo company manufacturing
• C3 Defense
• Charles Daly firearms
• Colt's Manufacturing Company
• CMMG
• Crusader Weaponry
• Daniel Defence
• Diemaco/Colt Canada
• Doublestar Corp
• DPMS Panther Arms
• LAR Grizzly manufacturing
• Heckler and Koch
• High Standard Manufacturing Company
• Izhmash/Molot Russia (rumored)
• Les Baer
• Lewis Machine and Tool Company
• LWRC International
• Norinco (China)
• Oberland Arms
• Olympic Arms
• Para-USA/Para Ordnance
• POF-USA Patriot ordnance factory
• Remington Arms
• Rock River Arms
• Sabre Defence
• Sig Sauer
• Smith & Wesson
• Special Ops Tactical
• Spikes Tactical
• Stag Arms
• Sturm, Ruger
• Vulcan Armament
• Wilson Combat
• Windham Weaponry
• Z-M Weapons

See also

M4 carbine CAR-15 SR-47

C7 T65 assault rifle Bushmaster M4 Type Carbine

• .50 Beowulf
• XM177/GAU-5 series

References

1. ^ "M-16 Rifle also called AR-15". http://www.britannica.com/EBchecked/topic/353341/M16-rifle. Retrieved 2008-07-16. 
2. ^ "Infantry Weapons Used in Borneo". http://www.britains-smallwars.com/Borneo/borneo-weapons.html. Retrieved 2008-07-16. 
3. ^ "M-16/AR-15". http://www.websters-online-dictionary.com/definition/AR-15%252FM16. Retrieved 2008-07-16. 
4. ^ "Armalite AR-15". http://www.probertencyclopaedia.com/cgi-bin/res.pl?keyword=Armalite+AR-15&offset=0. Retrieved 2008-07-16. 
5. ^ "Colt AR-15". http://www.coldwarshooters.net/index.php?main_page=product_info&cPath=11&products_id=627. Retrieved 2008-07-16. ^{[dead link]}
6. ^ "ARMALITE AR-15". http://www.probertencyclopaedia.com/F_ARMALITE_AR-15.HTM. Retrieved 2008-07-16. 
7. ^ "Colt Model AR6721". http://www.eastcoastfirearms.com/sub/page.asp?page_id=42. Retrieved 2008-07-16. 
8. ^ Blue Book Publications – COLT'S MANUFACTURING COMPANY, LLC AR-15, Pre-Ban, 1963–1989 Mfg. w/Green Label Box. Store.bluebookinc.com. Retrieved on 2011-09-27.
9. ^ ^{a b} "A Historical Review of Armalite" (PDF). ArmaLite, Inc.. 1999-04-23. http://www.armalite.com/images/Library/AL%20HISTORY%20COPY%202.pdf. Retrieved 2008-07-16. 
10. ^ p.96 Dockery, Kevin Future Weapons Berkley Books, 2007
11. ^ "AR-15 Carbine". http://www.olyarms.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=17&category_id=7&manufacturer_id=0&option=com_virtuemart&Itemid=37&vmcchk=1&Itemid=37. Retrieved 2008-07-16. 
12. ^ ^{a b} "Lightning Link Page". http://www.quarterbore.com/nfa/lightninglink.html. Retrieved 2009-05-10. 
13. ^ "Drop in Auto-Sear Page". http://www.quarterbore.com/nfa/dias.html. Retrieved 2009-05-10. 
14. ^ U.S. Military Small Arms Ammunition Failures and Solutions, GK Roberts, NDIA Dallas, TX, 21 May 2008 http://www.dtic.mil/ndia/2008Intl/Roberts.pdf
15. ^ Evolution of an AR | Gear | Guns & Ammo. Archives.gunsandammo.com (2011-08-29). Retrieved on 2011-09-27.
16. ^ Miller, Don. How Good Are Simple Rules For Estimating Rifling Twist, Precision Shooting – June 2009
17. ^ Firearms Safety Training, Canadian Firearms Centre (CFC)
18. ^ List of Restricted and Prohibited Firearms, Canadian Firearms Centre (CFC)
19. ^ "RCMP Firearms Program Regulations on Transporting Firearms". Rcmp-grc.gc.ca. 2007-04-20. http://www.rcmp-grc.gc.ca/cfp-pcaf/faq/trans-eng.htm#d1. Retrieved 2009-11-28. 
20. ^ "ATF Online — Firearms FAQs (section O, question 1)". ATF. 2006-07-06. http://www.atf.gov/firearms/faq/faq2.htm#o2. Retrieved 2007-01-23. ^{[dead link]}
21. ^ "ATF Online — Firearms FAQs (section O, question 11)". ATF. 2006-07-06. http://www.atf.gov/firearms/faq/faq2.htm#o11. Retrieved 2007-01-23. ^{[dead link]}
22. ^ http://ag.ca.gov/firearms/forms/pdf/awguide.pdf
23. ^ California Penal Code § 12020(a)(2),(b).
24. ^ "ATF ruling 07-07-2009" (PDF) (Press release). 2009. http://www.atf.gov/press/releases/2009/07/070709-openletter-ffl-gca.pdf. 
25. ^ TC V. U.S. 91–164. Caselaw.lp.findlaw.com. Retrieved on 2011-09-27.
26. ^ "ArmaLite, Inc. Technical Note – 5.56 NATO vs SAAMI .223 Chambers". ArmaLite, Inc.. 2002-12-04. Archived from the original on 2006-12-17. http://web.archive.org/web/20061217132137/http://www.armalite.com/library/techNotes/tnote45.htm. Retrieved 2007-01-23. 
27. ^ "ArmaLite, Inc. Technical Note — Prevention of Slamfires". ArmaLite, Inc.. 1998-12-26. http://www.armalite.com/images/Tech%20Notes%5CTech%20Note%2010,%20Prevention%20of%20Slamfires%20981226.pdf. Retrieved 2009-02-19. 

External links

• Modern Firearms article
• Technical explanation of direct gas impingment operation as it relates to the AR-15