Adopted in July 1997, the M16A4 is the fourth generation of the M16 series. The M16A2 fires the improved 5.56×45mm (M855/SS109) cartridge and has a newer adjustable rear sight, case deflector, heavy barrel, improved handguard, pistol grip and buttstock, as well as a semi-auto and three-round burst fire selector.
In 1983, the US Marine Corps adopted the M16A2 rifle and the US Army adopted it in 1986. The M16A1's improvements include a bolt-assist, chrome-plated bore and a 30-round magazine. In 1969, the M16A1 replaced the M14 rifle to become the US military's standard service rifle. In 1964, the M16 entered US military service and the following year was deployed for jungle warfare operations during the Vietnam War. The original M16 rifle was a 5.56×45mm assault rifle with a 20-round magazine. The M16 rifle (officially designated Rifle, Caliber 5.56 mm, M16) is a family of military rifles adapted from the ArmaLite AR-15 rifle for the United States military. It is marked on top with "2.5 x 10/inverted triangle inside a circle, (manufacturers code)/99 No.2578". As noted, it comes with the correct style Type 99 cutback scope. The underside of the stock has two Nagoya Army Arsenal inspection marks, with no drain hole in front of the trigger guard and a cupped sheet metal buttplate. It is fitted with its original hardwood stock and handguard with a matching numbered front barrel band, unnumbered middle band and front band with finger grooves on the sides. It has the standard front and rear sights without anti-aircraft wings. It is fitted with its complete matching original bolt assembly that is numbered on the underside "994" with a matching extractor, firing pin, and safety.
The rear ring is stamped with the symbol for the Nagoya Army Arsenal over serial number "6994". The chrysanthemum has been removed from the receiver ring however, the Kana markings (for Type 99) remain. The scope are also identified by the fact that they have a larger 1/4 inch rear edge on the scope mount (to fit the base), and the top of the tube is correctly marked "99". This was done before they introduced the newly developed 4x sniper scope.
The rear edge of the has been cutback 1/4 of an inch so that the Nagoya Arsenal could use up the old style 2.5x sniper scope from the Type 97 production. They very rare to find today as most were destroyed after the war, and they can be identified by the type of sniper scope base fitted the receiver.
This series of sniper rifles was produced on an extremely limited basis with only approximately 2,500 produced in total in the 5000-7500 serial number block. The Type 99 fired the larger, heavier 7.7 mm bullet. The Type 99 rifle was adopted in 1939 as a replacement for the previous Type 38, 6.5 mm rifles.
This is a solid representative example of a very rare mid-WWII production Japanese type 99 "cutback" sniper, fitted with a 2.5x sniper scope.