6th Battalion, 31st Infantry Sniper, identified as Sgt. Waldron, with M21 Sniper Rifle, Vietnam, 1969. Sergeant Adelbert F. Waldron, III had 109 confirmed kills to his credit, including a 900 meter kill of a Viet Cong sniper from a moving Riverine Boat on the Mekong River. Weapon is M-21 7.62mm Sniper Rifle.
The Rifle, 7.62mm, Sniper, M21 began as a the prototype XM21, developed jointly by the Army Weapons Command (Rock Island, IL), Combat Development Command (Ft. Benning, GA), and the Limited Warfare Agency (Aberdeen, MD). The XM21 was an accurized M14 National Match (NM) semi-automatic rifle equipped with a Leatherwood 3X-9X Adjustable Ranging Telescope (ART).
The Rock Island Arsenal converted 1,435 M14NM rifles to XM21 sniper rifles for initial fielding to Vietnam in 1969. The rifle originally had a hardwood stock, walnut impregnated with an epoxy, which was later replaced with a fiberglass stock. The XM21 was officially type classified M21 in 1975, though it had been informally called the M21 since December 1969. It was the primary Army sniper rifle of the Vietnam war and remained standard until formally replaced by the bolt-action M24 Sniper Weapon System beginning in 1988. The M21 remained in use in the Army and other services long after the introduction of the M24 (photo below).
Rifle, 7.62mm, Sniper, M21 in use in Afghanistan, 10 March 2004. Sniper is positioned on top of a HMMWV mounted Avenger Air Defense System. Thanks to Bob Pettit for discovering this U.S. Army photo.
The M21 was accurate to 750 yards (690m) due to hand-made improvements over the standard M14. The changes and upgrades included:
The barrel was gauged and selected to ensure correct specification tolerances. The bore was not chromium plated.
The receiver was individually custom fitted to the stock with a fiberglass compound.
The firing mechanism was reworked and polished to provide for a crisp hammer release. Trigger weight was between 4.5 to 4.75 pounds.
The suppressor was fitted and reamed to improve accuracy and eliminate any misalignment.
The gas cylinder and piston were reworked and polished to improve operation and to reduce carbon buildup.
The gas cylinder and lower band were permanently attached to each other.
Other parts were carefully selected, fitted, and assembled.
The M21 is described in TM 9-1005-223-10 and other manuals for the M14 rifle, as well as in Appendix B of FM 23-10 "Sniper Training".
M21 Sniper Rifle Ammunition
The M21 Sniper Rifle used U.S. match grade M118 NATO 7.62mm cartridges, in five-round or 20-round magazines. The M21 can fire long-range ball, ball/tracer and armor piercing (AP) ammunition. Long-range ammunition is produced to stringent tolerances to ensure superior accuracy. AP ammunition enables snipers to penetrate hard cover, such as urban terrain and light armor. The AP (black tip) round can penetrate 20mm of hardened steel at 100 meters.
The long-range ball ammunition uses the M118 bullet, a special 173 grain boat-tailed ball bullet consisting of a lead slug with a gilding metal jacket. The tip of the bullet is not colored. The base of the cartridge is stamped with the year of manufacture and a circle that has vertical and horizontal lines, sectioning it into quarters. Its spread for a 10-shot group is no more than 12 inches at 550 meters (fired from an accuracy barrel in a test cradle).
M21 Sniper Rifle Scopes and Optics
The M21 sniper weapon system is equipped with National Match rear sights, normally replaced by the telescope.
The M21 Sniper Rifle was equipped with a Leatherwood 3X-9X Adjustable Ranging Telescope (ART). The ART telescope featured adjustable ranging between 300m and 900m. This adjustable ranging feature removed much of the guesswork from aiming at the target. The ART was ballistically matched with U.S. M118 NATO ammunition.
The ART is based on a commercially procured telescopic scopesight, modified for use with the sniper rifle. This scope has a modified reticle with a ballistic earn mounted to the power adjustment ring on the ART I. The ART II has a separate ballistic cam and power ring. The ART is mounted on a spring-loaded base mount that is adapted to fit the M21.
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