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US Army M21 Sniper Rifle

US Army M21 Sniper Rifle
The M21 sniper rifle was developed during Vietnam and remained the standard issue US Army sniper rifle until 1988. It was based upon the M14 National Match.

Due to the USMC’s impressive PR campaign I’m sure many readers would just assume the top sniper during our war in Vietnam was a Marine wielding an M40. However, the truth may surprise you. Not only was a relatively unknown US Army Staff Sergeant the highest scoring sniper in Vietnam, but he did it with a semi-automatic M21. Credited with 109 kills Staff Sergeant Adelbert Waldron proved an M14 based sniper rifle could run with the USMC’s Model 70 Winchester target rifles and newer Remington M40 sniper rifles in actual combat. As a member of Company B, 3d Battalion, 60th Infantry Regiment of the 9th Infantry Division he found himself hunting with the ‘Brown Water’ Navy in the Mekong Delta. His feats included nine kills in one night using an AN/PVS-2 Starlight scope and a 900 meter shot from a moving naval vessel.

US Army M21 Sniper Rifle
Mounted to the side of the M21 was a unique 3-9x40mm ART scope.

The sniper rifle he carried was a M14 National Match topped with a 3-9x Adjustable Ranging Telescope (ART). This combination would later be designated the M21. The M21 was developed during Vietnam and remained the standard US Army sniper rifle until replaced by the bolt-action M24 in 1988. The M21 sniper rifle itself though was little more than a M14 built to National Match specifications topped with a scope. An offshoot of a straight competition rifle, the US Army sniper program benefited directly from technology developed by the ‘yellow glasses’. Selected rifles received match grade barrels, unitized gas systems, trimmed handguards, reamed flash suppressors, triggers were adjusted to slightly over 4.5 pounds, National Match sights were fitted and actions glass bedded.

US Army M21 Sniper Rifle
Sergeant Adelbert Waldron was the top scoring US sniper in Vietnam with 109 kills. He is seen here with his XM-21 sniper rifle.

Mounted to the side of the receiver was a unique sniper scope, the ART. Designed by Captain James R. Leatherwood and manufactured by Redfield, this optic allowed a sniper to easily range a man by zooming the magnification in or out until he fit between two marks on the reticle. Simultaneously the magnification ring cammed the scope up or down, automatically adjusting the range. So all the sniper had to do was bracket his target (which automatically adjusted the elevation), adjust for wind/lead and fire. It proved to be a very fast and simple system to use under actual battlefield conditions. In addition the 7.62x51mm 173 grain FMJ-BT M118 National Match load became standard issue for snipers. This competition load offered a dramatic step up in accuracy over standard 147 grain M80 ball. 

US Army M21 Sniper Rifle
A 25th Infantry Division sniper is seen here in Vietnam wielding an XM21 sniper rifle outfitted with an AN/PVS-2 Starlight scope and Sionics sound suppressor. This was state of the art at the time.

While a good rifle, the M21 had its weak points. Namely the 3-9x ART scope was insufficiently rugged and the rifle required a well trained honest to God armorer to properly maintain it. It fell out of favor after the lessons of Vietnam had been forgotten, only to be pressed back into service in Afghanistan and Iraq.


US Army M21 Sniper Rifle Specifications

Action Type: Short-stroke gas with rotating bolt
Caliber: 7.62x51mm NATO
Capacity: 20 round detachable box magazine
Barrel: 22 inches 1-11.25 inch twist
Overall Length: 44 inches
Weight: 11.5 pounds
Stock: Hardwood with glass bedding
Finish: phosphate
Trigger: 4.5 pound pull per National Match specifications
Iron Sights: NM post front, hooded NM rear
Optical Sight: 3-9x Adjustable Ranging Telescope and ART II
Dedicated Sniper Load: 173 grain FMJ-BT M118 National Match

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