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An AR-15-style rifle is any lightweight semi-automatic rifle based on the Colt AR-15 design. The original ArmaLite AR-15 is a scaled-down derivative of Eugene Stoner's ArmaLite AR-10 design. The then Fairchild Engine and Airplane Corporation division ArmaLite sold the patent and trademarks to Colt's Manufacturing Company in 1959. After most of Colt's patents for the Colt AR-15 expired in 1977, many firearm manufacturers began to produce copies of the Colt AR-15 under various names. While the patents expired, Colt retained the trademark of the AR-15 and is the sole manufacturer able to label their firearms as AR-15.^[1] The "AR" in Colt AR-15 stands for "ArmaLite Rifle", not "assault rifle".^[2]^[3]

The Federal Assault Weapons Ban restricted the sale of the Colt AR-15 and some derivatives in the United States from 1994 to 2004, although it did not affect rifles with fewer listed features.^[4]^[5] After the term modern sporting rifles was coined in 2009 by the US National Shooting Sports Foundation, a firearms trade association, it was quickly adopted by much of the industry.^[6]^[7]

In the 2010s, AR-15-style rifles became one of the "most beloved and most vilified rifles" in the United States, according to The New York Times. The rifles are controversial in part due to their use in high-profile mass shootings.^[8] Promoted as "America's rifle" by the National Rifle Association, AR-15-style rifles' popularity is partially attributable to active restrictions, or proposals to ban or restrict them.^[9]^[10]^[11]

Terminology

A common misconception is that "AR" is an acronym for "assault rifle",^[12] perhaps because of the weapon's inclusion in the Federal Assault Weapons Ban in 1994 or because the ArmaLite AR-15 was designed by infantry rifle designer Eugene Stoner to replace the M14 rifle in the Vietnam War.^[13] The "AR" in AR-15 stands for "ArmaLite Rifle".^[14]

The Colt AR-15 is closely related to the military M16 and M4 Carbine rifles, which all share the same core design, first patented for use in the AR-10, featuring a gas-operated, rotating bolt (combined with an integral piston) instead of conventional direct impingement, operating system patented under U.S. patent 2,951,424 by Eugene Stoner.^[15]^[16] The term "AR-15" is now most-commonly used to refer only to the civilian variants of the rifle which lack the fully automatic function.^[17]

1973 Colt AR-15 SP1 rifle with 'slab side' lower receiver (lacking raised boss around magazine release button) and original Colt 20-round box magazine

In 1956, ArmaLite designed a lightweight selective fire rifle for military use and designated it the ArmaLite model 15, or AR-15.^[18]^[13] Due to financial problems and limitations in terms of manpower and production capacity, ArmaLite sold the design and the AR-15 trademark along with the ArmaLite AR-10 to Colt's Manufacturing Company in 1959.^[19] In 1964, Colt began selling its own version with an improved semi-automatic design known as the Colt AR-15.^[20] After Colt's patents expired in 1977, an active marketplace emerged for other manufacturers to produce and sell their own semi-automatic AR-15 style rifles.^[1] Some versions of the AR-15 were classified as "assault weapons" and banned under the Public Safety and Recreational Firearms Use Protection Act in 1994 within the United States. This act expired in 2004.^[4]^[21]

In 2009, the term "modern sporting rifle" was coined by the National Shooting Sports Foundation for its survey that year as a marketing term used by the firearms industry to describe modular semi-automatic rifles including AR-15s.^[22]^[6]^[23]^[17] Today, nearly every major firearm manufacturer produces its own generic AR-15 style rifle.^[24]^[23] As Colt continues to own and use the AR-15 trademark for its line of AR-15 variants, other manufacturers must use their own model numbers and names to market their AR-15 style rifles for commercial sale.^[25]

Under US law, when manufactured with a barrel length less than 16 inches (410 mm) and without a shoulder stock, it is legally considered a pistol as opposed to being a short-barreled rifle,^[26] and is described as an AR-15 style pistol.

Modularity and customization

While most earlier breech-loading rifles had a single receiver housing both the trigger and reloading mechanism, an innovative feature of the AR-15 was modular construction to simplify substitution of parts and avoid need for arsenal facilities for most repairs of malfunctioning military rifles.^[27] A distinctive two-part receiver is used by both military and sporting AR-15 style rifles. As civilian ownership of AR-15 style rifles became sufficient to create a market for improvements, numerous manufacturers began producing aftermarket parts—including parts with features not found on basic AR-15 rifles, and individuals with basic mechanical aptitude can often substitute these pieces for original equipment without needing a gunsmith. Due to the vast assortment of aftermarket parts and accessories available, AR-15 style rifles have also been referred to as "the Swiss Army knife of rifles,"^[28] "Barbie Dolls for Guys,"^[29]^[30] or "LEGOs [sic] for adults".^[31]^[32]^[33] These more or less interchangeable modules are a defining characteristic of AR-15 style rifles.^[34]

The lower receiver is the part legally defined as the firearm under United States law. However, this definition is currently questionable due to several court rulings (or government dismissals to avoid rulings) that the AR-15 lower receiver does not match the legal definition in 27 CFR § 479.11,^[36]^[37]^[38] though a 2021 case from the Eighth Circuit found otherwise.^[39] A completed lower receiver is visually distinguished by the trigger guard ahead of the detachable pistol grip, and behind the magazine well capable of holding detachable magazines. The lower receiver holds the trigger assembly including the hammer, and is the attachment point for the buttstock. The lower receiver is attached to the upper receiver by two removable pins. Disassembly for cleaning or repair of malfunctions requires disengaging these pins from the upper receiver. Removal of the rear take-down pin allows the receiver to be opened by rotation around the forward pivot pin as a hinge.^[27]

The upper receiver contains the bolt carrier assembly and is attached to the barrel assembly. Sights may be attached to the upper receiver or the barrel assembly. A handguard usually encloses the barrel and is attached to the upper receiver, and depending on the handguard, also attached to the barrel's gas block.^[27]

Folding stocks

AR-15 style rifles may have folding or collapsible stocks which reduce the overall length of the rifle when folded, although some designs of the stock folding device may not allow the firearm to be fired until unfolded, or only fire once until unfolded.^[40] A few manufacturers have made full upper receivers^[41], or even "bufferless" bolt carrier systems where the buffer system is wholly contained in the upper receiver, and therefore does not use the buffer tube, which allows for firing while the stock is in the folded position, or removal of the stock altogether.^[42]

Gas systems

The standard design includes a gas block and tube to vent burnt powder gas back into the bolt carrier assembly where it expands in a variable volume chamber forcing the bolt open to eject the spent cartridge case. The buffer spring in the buttstock then pushes the bolt closed after picking up a new cartridge from the magazine. This Stoner bolt and carrier piston system has the disadvantage of venting un-burned smokeless powder residue into the receiver where it may ultimately accumulate in quantities causing malfunctions. Some AR-15 style rifles use an alternative short-stroke gas piston design borrowed from the AR-18, where a metal rod pushes against the bolt carrier, driven by a piston located just behind the barrel gas port. This piston design keeps the rifle cleaner by not exhausting in to the receiver.^[43] Some AR15-style rifle models feature redesigned gas systems so the rifle is over-the-beach capable to let it fire safely as quickly as possible after being submerged in water.^[44]^[45] The original design features a free-floating firing pin. To reduce the risk of slam-firing, some AR15-style rifle models feature a (proprietary) firing pin safety in the bolt. Such firing pin safeties can obstruct the upper to work with standard AR-15 type full height hammers in the fire control group of the lower.^[46]

Left-handed users

Most rifles eject spent cartridges from the right side of the receiver away from right handed shooters who place the butt against the right shoulder while sighting with the right eye and using a finger of the right hand to pull the trigger.^[47] Right-side ejection is a disadvantage for the third of the population whose left eye is dominant,^[48] and for the tenth of the population who are left handed,^[49] because holding these rifles against their left shoulder for maximum accuracy causes the rifle to eject hot spent cases toward the chest, neck or face of a left handed shooter.^[50] When the M16A2 was adopted by the Army in 1986, it incorporated a built-in brass deflector to prevent that happening. Most civilian-legal variants also copy that feature.^[51] The modular design of AR-15 style rifles has encouraged several manufacturers to offer specialized parts including leftward ejecting upper receivers and left-handed bolts/bolt carriers for converting right handed AR-15 style rifles for left handed use.^[52]^[53]^[54]

Calibers

The AR-15 is nominally chambered in .223/5.56mm NATO, but many variants have been produced in different calibers such as .22 LR, 7.62×39mm, 9×19mm Parabellum^[55],6.5mm Grendel, and shotgun calibers.^[56] Some of these firearms chambered in smaller calibers such as 9mm or .22 utilize simple blowback^[57] or delayed blowback^[58] operating principles instead of the default direct impingement/internal-piston based operating system, as insufficient gas pressure or volume is produced by the round to cycle the action, or the simpler blowback system is sufficient and may allow removal of the rear buffer tube and spring.

Compliance with state or local restrictions

Some AR-15-style rifles limit use of detachable magazines to comply with state regulations.^[59]^[60] Nearly all versions of the civilian AR-15 have a pistol grip like the military versions, but as the pistol grip is generally removable, grips that comply with various restrictions are available.^[61]

The FightLite SCR lower receiver is generally compatible with AR-15 upper receivers. It differs from the standard AR-15 lower receiver in that it uses a Monte Carlo stock instead of a pistol grip, which may allow it to be legally possessed in jurisdictions with assault weapon restrictions in place. It also uses a proprietary bolt carrier due to the angled buffer tube, and a proprietary fire control group that moves the trigger rearward.^[62] The AR-15 is banned in New York City, whereas the SCR has been approved.^[63]^[64]

A few manufactures offer bolt action or pump action^[65]^[66] AR-15-style rifles incapable of semi-automatic fire.^[67] These are most commonly marketed in jurisdictions where ownership of semi-automatic rifles is heavily restricted such as in the United Kingdom.

Comparison to military versions

The semi-automatic civilian AR-15 was introduced by Colt in 1963. The primary distinction between civilian semi-automatic rifles and military assault rifles is select fire. Military models were produced with firing modes, semi-automatic fire and either fully automatic fire mode or burst fire mode, in which the rifle fires several rounds in succession when the trigger is depressed. Most components are interchangeable between semi-auto and select fire rifles including magazines, sights, upper receiver, barrels and accessories.^[68]^[69] The military M4 carbine typically uses a 14.5-inch (37 cm) barrel. Civilian rifles commonly have 16-inch (41 cm) or longer barrels to comply with the National Firearms Act.^[70]

To prevent a civilian semi-automatic AR-15 from being readily converted for use with the select fire components, several features were changed. Parts changed include the lower receiver, bolt carrier, hammer, trigger, disconnector, and safety/mode selector. The semi-automatic bolt carrier has a longer lightening slot to prevent the bolt's engagement with an automatic sear. Due to a decrease in mass, the buffer spring is heavier. On the select-fire version, the hammer has an extra spur which interacts with the additional auto-sear that holds it back until the bolt carrier group is fully in battery, when the automatic fire is selected.^[71] Using a portion of the select fire parts in a semi-automatic rifle will not enable a select fire option (this requires a registered part with the ATF). Lower receivers that are select-fire are identified by a pinhole above the safety/mode selection switch.^[72]^[73]^[74]^[75] As designed by Colt the pins supporting the semi-auto trigger and hammer in the lower receiver are larger than those used in the military rifle to prevent interchangeability between semi-automatic and select-fire components.^[76]

Production and sales

The first version produced for commercial sale by Colt was the SP1 model AR-15 Sporter, in .223 Remington, with a 20-inch (51 cm) barrel and issued with five-round magazines.^[20] Initial sales of the Colt AR-15 were slow, primarily due to its fixed sights and carry handle that made scopes difficult to mount and awkward to use.^[77] Military development of the compact M4 carbine encouraged production of a 16-inch (41 cm) barreled civilian SP1 carbine with a collapsible buttstock beginning in 1977. These carbines have become popular for police use in confined urban spaces, and the collapsible buttstock compensates for the additional thickness of body armor. The shorter barrel reduced bullet velocity by about five percent, and bullet energy by about 10%. The shorter barrel required moving the gas port closer to the chamber, exposing the self-loading system to higher pressures and temperatures which increased stress on moving parts like the bolt lugs and extractor. Although Colt offered a heavier 20-inch barrel for improved accuracy beginning in 1986, increased barrel weight may impair ergonomic balance; so shorter barrels have dominated recent rifle production.^[78]

American Tactical OMNI AR-15 style rifle, (Lower in polymer), 5.56×45mm NATO caliber, with Millett DMS-1 scope and FAB Defense stock and grips

In the 1990s, sales of AR-15 style rifles increased dramatically, partly as a result of the introduction of the flat top upper receiver (M4 variant) which allowed scopes and sighting devices to be easily mounted as well as new features such as free floating hand guards that increased accuracy.^[77] While only a handful of companies were manufacturing these rifles in 1994, by the 21st century the number of AR-15 style rifles had more than doubled.^[79] From 2000 to 2015, the number of manufacturers of AR-15 style rifles increased from 29 to an estimated 500.^[80] AR-15 style rifles are now available in a wide range of configurations and calibers from a large number of manufacturers. These configurations range from standard full-sizes rifles with 20-inch (51 cm) barrels, to short carbine-length models with 16-inch (41 cm) barrels, adjustable length stocks and optical sights, to long range target models with 24-inch (61 cm) barrels, bipods and high-powered scopes.^[81]

In September 2019, Colt Firearms announced it was discontinuing production of the AR-15 for the consumer market, citing "significant excess manufacturing capacity" across the industry and the company's "high-volume contracts" with military and police forces that were "absorbing all of Colt's manufacturing capacity for rifles."^[82] However, in 2020 Colt resumed production of the AR-15, following a surge in demand in the United States consumer market.^[83]

Estimates vary as to how many of the rifles are owned in the United States. The National Shooting Sports Foundation has estimated that approximately 5 million to 10 million AR-15 style rifles exist in the U.S. within the broader total of the 300 million firearms owned by Americans.^[84]

Hunting

Many hunters prefer using AR-15 style rifles because of their versatility, accuracy, wide variety of available features, and wide variety of calibers (see below).^[85] Collapsible stocks are convenient for hunters who pack their rifles into remote hunting locations or for length of pull adjustments to fit any sized hunter.^[86] Construction with lightweight polymers and corrosion-resistant alloys makes these rifles preferred for hunting in moist environments with less concern about rusting or warping wood stocks. Positioning of the AR-15 safety is an improvement over traditional bolt action hunting rifles. Many states require hunters to use reduced-capacity magazines.^[87] If a hunter misses with a first shot, the self-loading feature enables rapid follow-up shots against dangerous animals like feral pigs or rapidly moving animals like jackrabbits.^[85] Hunters shooting larger game animals often use upper receivers and barrels adapted for larger cartridges or heavier bullets. Several states prohibit the use of .22 caliber cartridges like the .223 Remington on large game.^[88]^[89]^[90]

Cartridge variations

Since the upper and lower receivers may be swapped between rifles, forensic firearm examination of bullets and spent cartridges may reveal distinguishing marks from the barrel and upper receiver group without identifying the lower receiver for which legal records may be available.^[91] An individual may use several upper receiver groups with the same lower receiver. These upper receiver groups may have differing barrel lengths and sights and may fire different cartridges. A hunter with a single lower receiver might have one upper receiver with a .223 Remington barrel and telescopic sight for varmint hunting in the open country and another upper receiver with a .458 SOCOM barrel and iron sights for big-game hunting in brushy woodland. The dimensions of upper and lower receivers originally designed for the 5.56×45mm NATO cartridge impose an overall length limit and diameter limits when adapting modules for other cartridges included in this list of AR platform cartridges.^[92]^[81] The same magazine in the lower receiver group may hold differing numbers of different cartridges.^[43]

Use in crime and mass shootings

United States

Most firearm-related homicides in the United States involve handguns.^[93]^[94]^[95] A 2019 Pew Research study found that 4% of US gun deaths were caused by semi-automatic rifles, a category which includes AR-15 style rifles.^[96] According to a 2013 analysis by Mayors Against Illegal Guns, 14 out of 93 mass shootings involved high-capacity magazines or assault weapons.^[97] Nevertheless, AR-15 style rifles have played a prominent role in many high-profile mass shootings in the United States^[98] and have come to be widely characterized as the weapon of choice for perpetrators of these crimes.^[99] AR-15s or similar rifles were the primary weapons used in half of the 10 deadliest mass shootings in modern American history:^[100]^[101] the 2012 Sandy Hook Elementary School shooting, the 2017 Las Vegas shooting, the 2017 Sutherland Springs church shooting,^[102] the 2018 Stoneman Douglas High School shooting,^[103] and the 2022 Robb Elementary School shooting.^[104] Gun expert Dean Hazen and mass murder researcher Pete Blair think that mass shooters' gun choices have less to do with the AR-15's specific characteristics but rather with familiarity and a copycat effect.^[105]^[106]

Australia

Following the use of a Colt AR-15 rifle in the Port Arthur massacre, the worst single-person shooting incident in Australian history, the country enacted the National Firearms Agreement in 1996, restricting the private ownership of semi-automatic rifles. (Category D^[107]).^[108]^[109]^[110]

New Zealand

As a result of the Christchurch mosque shootings with an AR-15 during Friday Prayer on March 15, 2019, the New Zealand government enacted a law to ban semi-automatic firearms, magazines, and parts that can be used to assemble prohibited firearms.^[111]^[112]

Canada

After the 2020 Nova Scotia attacks, the deadliest rampage by a single person in Canadian history,^[113] Canada banned a class of rifles, including the AR-15.^[114]^[115]

Partial list of models

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^ O’Dea, Meghan (June 13, 2016). "What Makes the AR-15 So Appealing to Mass Shooters?". Fortune. Archived from the original on February 23, 2018. Retrieved February 15, 2018. While Colt alone makes the official AR-15, variants and knock-offs are made by a huge number of gun manufactures, including Bushmaster, Les Baer, Remington, Smith & Wesson (swhc, +0.00%), and Sturm & Ruger (rgr, -2.04%), just to name a few. TacticalRetailer claims that from 2000 to 2015 the AR manufacturing sector expanded from 29 AR makers to about 500, "a stunning 1,700% increase."
^ ^a ^b Evolution of an AR | Gear | Guns & Ammo Archived September 15, 2011, at the Wayback Machine. Archives.gunsandammo.com (August 29, 2011). Retrieved on September 27, 2011.
^ Jordan Valinsky (September 20, 2019). "Colt will stop making AR-15 rifles for consumers". CNN Business.
^ Chris Eger (June 29, 2020). "Colt Now Shipping AR-15s to Consumers again". Guns.com.
^ Schoen, John W. (June 13, 2016). "Owned by 5 million Americans, AR-15 under renewed fire after Orlando massacre". CNBC. Archived from the original on March 17, 2018. Retrieved March 17, 2018.
^ ^a ^b Drabold, Will. "Here Are 7 Animals Hunters Kill Using an AR-15". Time. Archived from the original on April 22, 2018. Retrieved May 22, 2018. In interviews with Time, leaders of 15 state shooting groups said semiautomatic rifles are popular with hunters in their states. Hunters say they favor the gun for its versatility, accuracy and customizable features for shooting animals. The semiautomatic feature, which allows these guns to shoot up to 45 rounds a minute, is not always necessary, but useful in some situations, hunters say.
^ Billings, Jacki. "Why hunters are trading in traditional hunting rifles for the AR-15". Guns.com. Archived from the original on May 20, 2018. Retrieved May 22, 2018.
^ Metcalf, Dick (April 30, 2012). "The AR for Deer Hunting?". North American Whitetail. Archived from the original on April 24, 2018. Retrieved May 24, 2018.
^ "Legal Hunting Weapons for Game Mammals". Oregon Hunting Regulations. J.F. Griffin Publishing. Archived from the original on August 3, 2018. Retrieved July 26, 2018.
^ "Legal Firearms for Hunting Big Game or Trophy Game Animals". Wyoming Hunter Ed Course. Kalkomey Enterprises LLC. Archived from the original on August 3, 2018. Retrieved July 26, 2018.
^ "Legal Use of Firearms and Archery Tackle". General Information & Hunting Regulations. Virginia Department of Game & Inland Fisheries. Archived from the original on August 3, 2018. Retrieved July 26, 2018.
^ Davis, Ann L. "How can a bullet be traced to a particular gun?". Scientific American. Archived from the original on March 1, 2018. Retrieved February 27, 2018.
^ U.S. Military Small Arms Ammunition Failures and Solutions, GK Roberts, NDIA Dallas, TX, May 21, 2008 "Archived copy" (PDF). Archived from the original (PDF) on June 28, 2011. Retrieved February 4, 2011.{{cite web}}: CS1 maint: archived copy as title (link)
^ "In Many U.S. States, 18 Is Old Enough to Buy a Semiautomatic". CBS News. The Associated Press. February 16, 2018. Archived from the original on February 20, 2018. Retrieved February 19, 2018. On average, more than 13,000 people are killed each year in the United States by guns, and most of those incidents involve handguns while a tiny fraction involve an AR-style firearm. Still, the AR plays an oversized role in many of the most high-profile shootings...
^ "Expanded Homicide Data Table 8". FBI. Retrieved June 3, 2022.
^ Balko, Radley (2013). Rise of the Warrior Cop: The Militarization of America's Police Forces. PublicAffairs. ISBN 978-1610392129.
^ "What the data says about gun deaths in the U.S." Pew Research Center. Retrieved May 31, 2021.
^ Todd, Michael (December 23, 2013). "The Simple Facts About Mass Shootings Aren't Simple at All". Pacific Standard. Archived from the original on August 23, 2018. Retrieved August 21, 2018.
^ Lisa Marie Pane And Brendan Farrington, Associated Press (February 15, 2018). "Florida shooting revives debate over gun age requirement - Business Insider". Uk.businessinsider.com. Retrieved May 2, 2020.
^ Jansen, Bart; Cummings, William (November 6, 2017), "Why mass shooters are increasingly using AR-15s", USA Today, archived from the original on February 15, 2018, retrieved February 15, 2018, AR-15 style rifles have been the weapon of choice in many recent mass shootings, including the Texas church shooting Sunday, the Las Vegas concert last month and the Orlando nightclub last year.
Oppel Jr., Richard A. (February 15, 2018), "In Florida, an AR-15 Is Easier to Buy Than a Handgun", The New York Times, archived from the original on February 15, 2018, retrieved February 15, 2018, The N.R.A. calls the AR-15 the most popular rifle in America. The carnage in Florida on Wednesday that left at least 17 dead seemed to confirm that the rifle and its variants have also become the weapons of choice for mass killers.
Lloyd, Whitney (February 16, 2018), Why AR-15-style rifles are popular among mass shooters, archived from the original on March 2, 2018, retrieved March 2, 2018, AR-15-style rifles have become something of a weapon of choice for mass shooters. {{citation}}: Unknown parameter |agency= ignored (help)
^ The Los Angeles Times identified five shootings including the Pulse Nightclub Shooting. Early reports on that shooting identified the rifle as an AR-15. Later reports noted that the rifle was a SIG MCX Howerton, Jason (June 14, 2016). "The gun the Orlando shooter used wasn't actually an AR-15". Business Insider. Archived from the original on October 6, 2018. Retrieved October 6, 2018., Gibbons-Neff, Thomas (June 14, 2016). "The gun the Orlando shooter used was a Sig Sauer MCX, not an AR-15. That doesn't change much". The Washington Post. Archived from the original on January 31, 2019. Retrieved October 6, 2018.
^ Pearce, Matt (February 14, 2018). "Mass shootings are getting deadlier. And the latest ones all have something new in common: The AR-15". Los Angeles Times. Archived from the original on May 10, 2018. Retrieved May 11, 2018. in all of the latest incidents...the attackers primarily used AR-15 semiautomatic rifles.
^ "Why the AR-15 keeps appearing at America's deadliest mass shootings". USA Today. Archived from the original on February 25, 2018. Retrieved February 22, 2018.
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^ Barned-Smith, St. John (May 25, 2022). "Uvalde teen gunman bought AR-15 style rifle day after he turned 18". Houston Chronicle. Retrieved May 25, 2022.
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^ "Nova Scotia mass killings: What we know and what we don't know". CBC News. April 19, 2020. Retrieved April 19, 2020. The suspect used his gun during the rampage, but may have used 'other methods' as well, said RCMP Chief Supt. Chris Leather.
^ "Canada Bans Assault-Style Weapons After Shooting Rampage". The New York Times. Associated Press. May 1, 2020. Retrieved May 2, 2020.
^ Ballingall, Alex (May 1, 2020). "Ottawa will let gun owners keep 'military-style' firearms despite nationwide ban". The Star. Retrieved May 2, 2020.

@@ Line 22: / Line 22: @@
 Under US law, when manufactured with a barrel length less than {{convert|16|in}} and without a shoulder stock, it is legally considered a pistol as opposed to being a [[short-barreled rifle]],<ref name="OL200416">{{cite web |author1=Chris Mudgett |title=7 Things You Need to Know Before Buying an AR Pistol |url=https://www.outdoorlife.com/story/hunting/things-to-know-before-buying-an-ar-pistol/ |website=Outdoor Life |access-date=March 25, 2021 |date=April 16, 2020}}</ref> and is described as an [[AR-15 style pistol]].
-== Modularity and operating systems ==
+==Modularity and customization==
-While most earlier [[Breech-loading weapon#Firearms|breech-loading rifles]] had a single [[Receiver (firearms)|receiver]] housing both the trigger and reloading mechanism, an innovative feature of the AR-15 was modular construction to simplify substitution of parts and avoid need for [[arsenal]] facilities for most repairs of malfunctioning military rifles.<ref name=colt>{{cite book |last=Colt |author-link =Colt's Manufacturing Company |title =M16A1 Rifle|publisher =[[Colt's Manufacturing Company]] |date =January 1980 |location =[[Hartford, Connecticut]] }}</ref> A distinctive two-part receiver is used by both military and sporting AR-15 style rifles. As civilian ownership of AR-15 style rifles became sufficient to create a market for improvements, numerous manufacturers began producing one or more "improved" modules, assemblies, or parts with features not found on factory rifles, and individuals with average mechanical aptitude can often substitute these pieces for original equipment. Due to the vast assortment of aftermarket parts and accessories available, AR-15 style rifles have also been referred to as "the Swiss Army knife of rifles,"<ref>Patrick Sweeney [http://www.lwrci.com/articles/GA-NOV-P48-55.pdf ARS Across the Board] {{webarchive|url=https://web.archive.org/web/20110819161911/http://www.lwrci.com/articles/GA-NOV-P48-55.pdf |date=August 19, 2011 }}. Guns & Ammo, November 2010</ref> "Barbie Dolls for Guys,"<ref>{{cite news|last1=Levings|first1=Darryl|title=AR-15 rifle more loved – and hated – than ever. Amid the rising call for the rifle to be banned, sales of the "Barbie doll for guys" have soared.|url=http://infoweb.newsbank.com/resources/doc/nb/news/144390DA1675E4A8?p=AWNB|access-date=August 10, 2016|work=Kansas City Star|date=February 2, 2013}}</ref><ref>{{cite book|last1=Kyle|first1=Chris|title=American Gun|date=2014|publisher=William Morrow Paperbacks|isbn=978-0062242723|page=252}}</ref> or "LEGOs {{sic}} for adults".<ref>{{Cite news|url=https://www.wired.com/2013/02/ar-15/|title=The AR-15 Is More Than a Gun. It's a Gadget|last=Stokes|first=Jon|newspaper=WIRED|language=en-US|access-date=January 30, 2017|archive-url=https://web.archive.org/web/20170202060008/https://www.wired.com/2013/02/ar-15/|archive-date=February 2, 2017|url-status=live}}</ref><ref>{{cite web|url=http://blog.cheaperthandirt.com/fifteen-cheap-ar-accessories/|title=Fifteen of the Best Cheap AR Accessories|website=The Shooter's Log|date=April 18, 2015|language=en-US|access-date=January 30, 2017|archive-url=https://web.archive.org/web/20170202071341/http://blog.cheaperthandirt.com/fifteen-cheap-ar-accessories/|archive-date=February 2, 2017|url-status=live}}</ref><ref>{{Cite news|url=http://ballisticadvantage.com/blog/lego-kits-for-adults/|title=Lego Kits for Adults|date=July 13, 2016|newspaper=AR Blog|language=en-US|access-date=January 30, 2017|archive-url=https://web.archive.org/web/20170202060024/http://ballisticadvantage.com/blog/lego-kits-for-adults/|archive-date=February 2, 2017|url-status=live}}</ref> These more or less [[Interchangeable parts|interchangeable modules]] are a defining characteristic of AR-15 style rifles.<ref>{{cite web |url=https://www.nssf.org/msr/ |title=Modern Sporting Rifle |publisher=[[National Shooting Sports Foundation]] |access-date=February 27, 2018 |archive-url=https://web.archive.org/web/20171228133617/https://www.nssf.org/msr/ |archive-date=December 28, 2017 |url-status=live  }}</ref>
+While most earlier [[Breech-loading weapon#Firearms|breech-loading rifles]] had a single [[Receiver (firearms)|receiver]] housing both the trigger and reloading mechanism, an innovative feature of the AR-15 was modular construction to simplify substitution of parts and avoid need for [[arsenal]] facilities for most repairs of malfunctioning military rifles.<ref name=colt>{{cite book |last=Colt |author-link =Colt's Manufacturing Company |title =M16A1 Rifle|publisher =[[Colt's Manufacturing Company]] |date =January 1980 |location =[[Hartford, Connecticut]] }}</ref> A distinctive two-part receiver is used by both military and sporting AR-15 style rifles. As civilian ownership of AR-15 style rifles became sufficient to create a market for improvements, numerous manufacturers began producing aftermarket parts—including parts with features not found on basic AR-15 rifles, and individuals with basic mechanical aptitude can often substitute these pieces for original equipment without needing a gunsmith. Due to the vast assortment of aftermarket parts and accessories available, AR-15 style rifles have also been referred to as "the Swiss Army knife of rifles,"<ref>Patrick Sweeney [http://www.lwrci.com/articles/GA-NOV-P48-55.pdf ARS Across the Board] {{webarchive|url=https://web.archive.org/web/20110819161911/http://www.lwrci.com/articles/GA-NOV-P48-55.pdf |date=August 19, 2011 }}. Guns & Ammo, November 2010</ref> "Barbie Dolls for Guys,"<ref>{{cite news|last1=Levings|first1=Darryl|title=AR-15 rifle more loved – and hated – than ever. Amid the rising call for the rifle to be banned, sales of the "Barbie doll for guys" have soared.|url=http://infoweb.newsbank.com/resources/doc/nb/news/144390DA1675E4A8?p=AWNB|access-date=August 10, 2016|work=Kansas City Star|date=February 2, 2013}}</ref><ref>{{cite book|last1=Kyle|first1=Chris|title=American Gun|date=2014|publisher=William Morrow Paperbacks|isbn=978-0062242723|page=252}}</ref> or "LEGOs {{sic}} for adults".<ref>{{Cite news|url=https://www.wired.com/2013/02/ar-15/|title=The AR-15 Is More Than a Gun. It's a Gadget|last=Stokes|first=Jon|newspaper=WIRED|language=en-US|access-date=January 30, 2017|archive-url=https://web.archive.org/web/20170202060008/https://www.wired.com/2013/02/ar-15/|archive-date=February 2, 2017|url-status=live}}</ref><ref>{{cite web|url=http://blog.cheaperthandirt.com/fifteen-cheap-ar-accessories/|title=Fifteen of the Best Cheap AR Accessories|website=The Shooter's Log|date=April 18, 2015|language=en-US|access-date=January 30, 2017|archive-url=https://web.archive.org/web/20170202071341/http://blog.cheaperthandirt.com/fifteen-cheap-ar-accessories/|archive-date=February 2, 2017|url-status=live}}</ref><ref>{{Cite news|url=http://ballisticadvantage.com/blog/lego-kits-for-adults/|title=Lego Kits for Adults|date=July 13, 2016|newspaper=AR Blog|language=en-US|access-date=January 30, 2017|archive-url=https://web.archive.org/web/20170202060024/http://ballisticadvantage.com/blog/lego-kits-for-adults/|archive-date=February 2, 2017|url-status=live}}</ref> These more or less [[Interchangeable parts|interchangeable modules]] are a defining characteristic of AR-15 style rifles.<ref>{{cite web |url=https://www.nssf.org/msr/ |title=Modern Sporting Rifle |publisher=[[National Shooting Sports Foundation]] |access-date=February 27, 2018 |archive-url=https://web.archive.org/web/20171228133617/https://www.nssf.org/msr/ |archive-date=December 28, 2017 |url-status=live  }}</ref>
 [[File: AR replacement parts.jpg|thumb|A stripped lower receiver, one that is lacking the additional parts included in a completed lower receiver, is the only part of an AR-15 style rifle that needs to be transferred through a federally licensed firearms dealer under United States federal law.<ref>{{cite web |url=https://gunpros.com/best-ar-15-stripped-lower-receiver/ |title=10 Best AR-15 Stripped Lower Receiver for Your Needs &#91;2021 Review&#93; |access-date=February 22, 2019 |archive-url=https://web.archive.org/web/20190222151902/https://gunpros.com/best-ar-15-stripped-lower-receiver/ |archive-date=February 22, 2019 |url-status=live }}</ref>]]
-The lower receiver is the serial-numbered part legally defined as the firearm under United States law. However, this definition is currently questionable due to several court rulings (or government dismissals to avoid rulings) that the AR-15 lower receiver does not match the legal definition in 27 CFR § 479.11,<ref>{{citation|author=JORDAN MICHAELS |title=Judge Finds Serious 'Disconnect' in ATF's Classification of AR-15 Lower Receivers as 'Firearms' |publisher=Guns America LLC}}</ref><ref>{{cite news |last1=GLOVER |first1=SCOTT |title=Former ATF agent at center of legal dispute over AR-15 |url=https://kslnewsradio.com/1919080/former-atf-agent-at-center-of-legal-dispute-over-ar-15/? |publisher=KSL News Radio |date=February 7, 2020}}</ref><ref>{{cite news |last1=BLEIBERG |first1=JAKE |last2=DAZIO |first2=STEFANIE |title=Design of AR-15 could derail charges tied to popular rifle |url=https://apnews.com/article/396bbedbf4963a28bda99e7793ee6366 |publisher=AP News |date=January 13, 2020}}</ref> though a 2021 case from the Eighth Circuit found otherwise.<ref>{{Cite web|title=United States v. Burning Breast, No. 20-1450 (8th Cir. 2021)|url=https://law.justia.com/cases/federal/appellate-courts/ca8/20-1450/20-1450-2021-08-11.html|access-date=September 16, 2021|website=Justia Law|language=en}}</ref> A completed lower receiver is visually distinguished by the [[trigger guard]] ahead of the detachable [[pistol grip]], and behind the magazine well capable of holding detachable magazines. The lower receiver holds the [[Trigger (firearms)|trigger]] assembly including the [[Hammer (firearms)|hammer]], and is the attachment point for the [[buttstock]]. The lower receiver is attached to the upper receiver by two removable pins. Disassembly for cleaning or repair of malfunctions requires disengaging these pins from the upper receiver. Removal of the rear take-down pin allows the receiver to be opened by rotation around the forward pivot pin as a [[hinge]].<ref name=colt/>
+The lower receiver is the part legally defined as the firearm under United States law. However, this definition is currently questionable due to several court rulings (or government dismissals to avoid rulings) that the AR-15 lower receiver does not match the legal definition in 27 CFR § 479.11,<ref>{{citation|author=JORDAN MICHAELS |title=Judge Finds Serious 'Disconnect' in ATF's Classification of AR-15 Lower Receivers as 'Firearms' |publisher=Guns America LLC}}</ref><ref>{{cite news |last1=GLOVER |first1=SCOTT |title=Former ATF agent at center of legal dispute over AR-15 |url=https://kslnewsradio.com/1919080/former-atf-agent-at-center-of-legal-dispute-over-ar-15/? |publisher=KSL News Radio |date=February 7, 2020}}</ref><ref>{{cite news |last1=BLEIBERG |first1=JAKE |last2=DAZIO |first2=STEFANIE |title=Design of AR-15 could derail charges tied to popular rifle |url=https://apnews.com/article/396bbedbf4963a28bda99e7793ee6366 |publisher=AP News |date=January 13, 2020}}</ref> though a 2021 case from the Eighth Circuit found otherwise.<ref>{{Cite web|title=United States v. Burning Breast, No. 20-1450 (8th Cir. 2021)|url=https://law.justia.com/cases/federal/appellate-courts/ca8/20-1450/20-1450-2021-08-11.html|access-date=September 16, 2021|website=Justia Law|language=en}}</ref> A completed lower receiver is visually distinguished by the [[trigger guard]] ahead of the detachable [[pistol grip]], and behind the magazine well capable of holding detachable magazines. The lower receiver holds the [[Trigger (firearms)|trigger]] assembly including the [[Hammer (firearms)|hammer]], and is the attachment point for the [[buttstock]]. The lower receiver is attached to the upper receiver by two removable pins. Disassembly for cleaning or repair of malfunctions requires disengaging these pins from the upper receiver. Removal of the rear take-down pin allows the receiver to be opened by rotation around the forward pivot pin as a [[hinge]].<ref name=colt/>
 The upper receiver contains the [[Bolt (firearms)|bolt]] carrier assembly and is attached to the [[Gun barrel|barrel]] assembly. [[Sight (device)|Sights]] may be attached to the upper receiver or the barrel assembly. A handguard usually encloses the barrel and is attached to the upper receiver, and depending on the handguard, also attached to the barrel's gas block.<ref name=colt/>