When the American military adopted the M16 rifle, established off the Armalite AR-15, an interest in customization and enhancements to the weapon worked on. After the AR-15 patents ended, an active marketplace emerged around the rifle's design of using an intermediate cartridge, a semi automatic system, STANAG magazines and interchangeable upper and lower receivers. Notable variations include replacing the original direct impingement gas operation with a long/short stroke piston operation, or using new cartridges like.300 AAC Blackout.
The prototype AR-15 was intended by ArmaLite as a selective fire weapon for military reasons. Armalite sold the design to Colt caused by financial difficulties. After some mods, it will sooner or later became the US Army's M16, with a civilian variant marketed as the Colt AR-15.
The term "AR-15" signifies "Armalite, design 15". The trademark "AR15" or "AR-15" is registered to Colt, which requires the term to be used only to refer to their merchandise. Colt uses "AR-15" for its semi automatic civilian guns and many use the term only for Colt AR-15s and clones made by other manufacturers. Other manufacturers make AR-15 clones and variants marketed under separate designations, though they are usually called AR-15s.
AR-15 variants are available in a large range of configurations from a big number of manufacturers. These configurations vary from short carbine length models with features like adjustable length stocks and optical sights, to finish redesigns for different roles like chosen marksman guns, varmint and submachine guns. caused by the countless alternatives, AR-15s have been called "Barbie Dolls for Guys" or "LEGOs" for adults.
Another common gun:
The lower receiver holds the trigger, disconnector, hammer and fire selector collectively called the fire control group , and in the U.S. The Bureau of Alcohol, Tobacco, Firearms and Explosives Technology Division designates the lower receiver as "firearms" and requires licensed manufacturers and importers to mark it with a serial number, their name and other markings. BATFE business functionings enforce the rules and rules that find out who is really in the firearms business and subject to licensing prerequisites, guideline and oversight.
AR-15 variants employ a modular design. one upper receiver can quickly and easily be substituted for another from the aftermarket. Many aftermarket upper receivers are available that integrate barrels of different weights, lengths and calibers. Available calibers include the.223 Remington, 5.5645mm NATO,.300 Blackout, 7.6239mm, 5.4539mm, 919mm Parabellum,.45 ACP, 5.728mm, 6.5mm Grendel, 6.8mm Remington SPC,.50 Beowulf and.458 SOCOM.
Early models had a 1:14 rate of turn for the original 55 grain 3.6 g bullets in.223 Remington sporting target and plinking rounds. This has been changed to 1:12 when it was found that in cold weather 1:14 was inadequate to stabilize the bullet, leaving a "keyhole" in paper targets. last models have faster rates of turn, rising from 1:9 to 1:7. The degree to which differing turn rates influence ballistics and terminal performance is controversial, though heavier, longer projectiles tend to do better with faster rifling rates. Competitive target shooting matches frequently use.223 Remington rounds, on occasion as heavy as 77gr, with Open Tip Match OTM points and tapered "boattail" bases to preserve accuracy in different conditions.
Heavy .223Rem rounds are impractical for military or hunting applications given the alternatives and are usually restricted to competitive target shooting. also, different calibers have their own common turn rate s, between 1:10 and 1:12 for 6.843mm SPC, 1:10 for 7.6239mm, 1:9 for 6.5 Grendel and 1:8 for.300 Blackout. specific barrels with gain twist rifling rates are available for competitive shooters that tune hand loaded target ammunition, varying powder burn rate, barrel length and bullet weight. This lets long barreled target rifles to use big powder loads with slow burn rates to keep the pressure in the barrel at its maximum capacity. This in turn accelerates the round to extreme velocity while maintaining constant angular momentum for stability. it's a technique borrowed from big bore guns.
Civilian models can not be legally changed to full auto in the United States. Today, the civilian make, sale and ownership of post-1986 select fire AR-15 variants or auto trigger group parts is banned, per the Hughes Amendment to the Firearm holders Protection Act, barring certain exempted groups like motion picture armorers. but, it's legal to sell templates, tooling and manuals to conduct such conversion. These things are usually marketed as "post sample" materials for Federal Firearm Licensees. They can be used to make select fire variants of the AR-15 for sale to law enforcement, military and abroad customers.
If you are wondering why this rifle is most popular:
In the late 1970s and early 1980s, conversion to full auto was straightforward, using things like the "Drop In Auto Sear" or "lightning link". In some cases such conversion obliged machining the lower receiver with a mill, also as the substitution of a M16 screw carrier group. changed weapons didn't thus become able to switch between the three modes of the military model. The latter obliged a special full auto fire choose system and a changed selector switch. Some AR-15's made before 1986 were legally transformed to M16s by gunsmiths as Form One. previous to 1986 a full auto variant cost $100 more than the semiautomatic type $600, after the NFA registry closed in 1986 these full auto guns soared in value to over $12,000.
FOPA redefined the meaning of a machine gun to include individual parts with which a semi automatic firearm may be transformed to full automatic depending on a 1981 ATF decision on machine gun parts. Since 1993, the screw carrier groups used in AR-15 type for civilians employed extra measures to prevent modification to full auto. Colt AR-15's use a metal alloy counter to separate the fire control group from the sear, preventing use of full auto parts.
