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How a AR-7 works
The ArmaLite AR-7 Explorer is a semi-automatic firearm in .22 Long Rifle caliber, developed in 1959 from the AR-5 that was adopted by the U.S. Air Force as a pilot and aircrew survival weapon. The AR-7 was adopted and modified by the Israeli Air Force as an aircrew survival weapon in the 1980s.
The AR-7 was designed by American firearms designer Eugene Stoner, who is most associated with the development of the ArmaLite AR-15 rifle that was adopted by the US military as the M16. The civilian AR-7's intended markets today are backpackers and other recreational users as a takedown utility rifle. The AR-7 is often recommended for use by outdoor users of recreational vehicles (automobile, airplane or boat) who might have need for a weapon for foraging or defense in a wilderness emergency.
The prototype of what would become the AR-7 was designed by Eugene Stoner at ArmaLite Inc., a division of Fairchild Aircraft. The rifle shares some of the features of the bolt-action AR-5, another takedown rifle designed by Stoner for ArmaLite and adopted by the United States Air Force in 1956 as the MA-1. The MA-1 was intended to replace the M4 Survival Rifle and the M6 Aircrew Survival Weapon which was a superposed ("over-under") twin-barrel rifle/shotgun chambered in .22 Hornet and .410 bore, using a break-open action. The AR-5 had the advantage of repeat fire over the then-standard M6, using the same .22 Hornet cartridge. When the AR-5 was adopted as the MA-1 but was not placed in issue due to the numbers of usable M4 and M6 survival weapons in USAF inventory, ArmaLite used the research and tooling for the AR-5 in developing the AR-7 for the civilian market.
The AR-7 uses a blowback semi-automatic action in .22 Long Rifle but retains the AR-5/MA-1 feature of storing the disassembled parts within the hollow stock, which is filled with plastic foam and capable of floating. Like the bolt-action AR-5, the AR-7 was designed as a survival rifle for foraging small game for food. The AR-7 is constructed primarily of aluminum, with plastic for the stock, buttcap, and recoil spring guide. The bolt is steel. The original barrel was aluminum using a rifled steel liner; barrels of some production models have used all steel barrels, others have used barrels made of composite materials. The AR-7 measures 35 inches overall when assembled. It disassembles to four sections (barrel, action, stock, and magazine), with three parts storing inside the plastic stock, measuring 16 inches long. The rifle weighs 2.5 pounds, light enough for convenient backpacking. The rear sight is a peep sight, which comes on a flat metal blade with an aperture (in later production two different size apertures available by removing and flipping the rear sight), and is adjustable for elevation (up-down). The front sight is adjustable for windage (side-to-side). Accuracy is sufficient for hunting small game at ranges to 50 yards.
Reliability of the AR-7 is highly dependent on the condition of the magazine and on the ammunition used, perhaps more so than with other models of semi-automatic .22 caliber rifles. The feed ramp is part of the magazine and subject to damage from mishandling. Flat-nosed bullets tend to jam on the edge of the chamber of the barrel. The transition of cartridge from magazine to barrel can be smoothed by minor beveling of the chamber of the barrel, by using round-nosed as opposed to flat-nosed bullets and by paying attention to condition of the feed lips and feed ramp of the magazine. Later production magazines include an external wire spring to align the cartridge; earlier magazines used two pinch marks at the top of the magazine body, which in use could become sprung open or worn.
All iterations of the AR-7 from the ArmaLite to the Henry U.S. Survival rifle use a bolt and dual recoil springs that are heavy compared to most other .22 semiautomatics. The AR-7 requires high velocity ammunition for reliable functioning. The manufacturers recommend use of 40 grain round nose bullets in high velocity loadings. It is possible to manually load a single round into the firing chamber, allowing use of flat nosed bullets or low velocity or subsonic ammunition.
The barrel takedown nut tends to loosen during firing and may need hand-tightening to maintain both accuracy and reliability.
ArmaLite sold the design to Charter Arms in 1973. According to some accounts posted by enthusiasts, this is when quality began to deteriorate. Barrels were said to have a tendency to warp. Other sources state that the first production at Charter had problems which were corrected in later production runs.