The United States Army Squad Designated Marksman Rifle (SDM-R) is a heavily modified

M16 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. The original M16 rifle was a 5.56×45mm automatic rifle with a 20-roun ...

-series rifle intended to provide increased accuracy at longer ranges, giving

infantry Infantry is a military specialization which engages in ground combat on foot. Infantry generally consists of light infantry, mountain infantry, motorized infantry & mechanized infantry, airborne infantry, air assault infantry, and marine i ...

squad In military terminology, a squad is among the smallest of military organizations and is led by a non-commissioned officer. NATO and US doctrine define a squad as an organization "larger than a team, but smaller than a section." while US Army do ...

s greater firepower. The SDM-R is designed to provide engagement capability at the squad level to 600 meters, similar to the needs expressed by members of

USSOCOM The United States Special Operations Command (USSOCOM or SOCOM) is the unified combatant command charged with overseeing the various special operations component commands of the Army, Marine Corps, Navy, and Air Force of the United States Ar ...

that led to the development of weapons such as the

Mk 12 Special Purpose Rifle The United States Navy Mk 12 MOD 0/1/H Special Purpose Rifle (SPR) is a designated marksman rifle that was in service with United States Special Operations Forces in the designated marksman role until 2017, also designed to be shorter than stand ...

(SPR) and the

SEAL Recon Rifle The SEAL Recon Rifle (also known as the "Sniper M4" and "Recce") is a heavily modified M16-series rifle intended to provide US Navy SEAL snipers with a versatile, accurate, lightweight, and relatively compact weapon chambered in 5.56×45mm NAT ...

History

The addition of an embedded

marksman A marksman is a person who is skilled in precision shooting using projectile weapons (in modern days most commonly an accurized scoped long gun such as designated marksman rifle or a sniper rifle) to shoot at high-value targets at longer-than-u ...

at the

platoon A platoon is a military unit typically composed of two or more squads, sections, or patrols. Platoon organization varies depending on the country and the branch, but a platoon can be composed of 50 people, although specific platoons may range ...

level has been a continuing process in the

U.S. military The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is the ...

. The U.S. Marine Corps (USMC) experimented with this during ''Project Metropolis'', before creating the "Squad Advanced Marksman" (SAM) position along with the Squad Advanced Marksman Rifle (SAM-R) specifically for this purpose. The 3rd Infantry Division followed suit in implementing a training program to have one marksman per squad, the Squad Designated Marksman (SDM), and developing a rifle, the Squad Designated Marksman Rifle (SDM-R). The SDM is an integral part of the squad and serves as a

rifleman A rifleman is an infantry soldier armed with a rifling, rifled long gun. Although the rifleman role had its origin with 16th century hand cannoneers and 17th century musketeers, the term originated in the 18th century with the introduction o ...

first and

designated marksman A designated marksman (DM), squad advanced marksman (AD) or squad designated marksman (SDM) is a military marksman role in an infantry squad. The term ''sniper'' was used in Soviet doctrine although the soldiers using the Dragunov SVD were the f ...

second. The SDM is not meant to be a squad

sniper A sniper is a military/paramilitary marksman who engages targets from positions of concealment or at distances exceeding the target's detection capabilities. Snipers generally have specialized training and are equipped with high-precision r ...

who engages the enemy with precision fire at long ranges, but instead is trained to directly support the squad with well-aimed shots at ranges slightly beyond the normal engagement distances for riflemen. Much like the U.S. Marine Corps SAM-R, the 3rd Infantry division SDM-R was an accurized

M16 rifle 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. The original M16 rifle was a 5.56×45mm automatic rifle with a 20-roun ...

built in-house by the

United States Army Marksmanship Unit The United States Army Marksmanship Unit (USAMU or AMU) is a part of U.S. Army providing small arms marksmanship training for soldiers and enhancing Army recruiting. The unit was originally established in 1956 at the direction of president Dwight ...

with 240 rifles provided for deployment in Iraq. The rifle was informally known as "the AMU rifle". The SAM-R was replaced from US Army service, mostly due to performance of match grade 5.56 NATO ammo in the DMR role. It was being replaced by the HK 417 as the army's new SDM rifle. Most were expected to be in service by 2020.

Training

The National Guard Marksmanship Training Center of the

Arkansas Army National Guard The Arkansas Army National Guard (ARARNG) is a component of the Arkansas National Guard and the United States National Guard. National coordination of various state National Guard units are maintained through the National Guard Bureau. Arkansas ...

conducts the fourteen-day-long Squad Designated Marksman Course at Camp Joseph T. Robinson. Soldiers fire over 1500-rounds from the M16A4 rifle under the close supervision of course cadre. Another is done in Fort Benning, Georgia. Task Force Small Arms Readiness Group (TF SARG) conducts the week-long SDM course at the SARG academy at

Camp Bullis Camp Bullis Military Training Reservation is a U.S. Army training camp comprising in Bexar County, Texas, USA, just northwest of San Antonio. Camp Bullis provides base operations support and training support to Joint Base San Antonio. The camp i ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

. Many of the instructors are President's 100 recipients.

Specifications

*The US Army used either M16A2 or A4 lower receivers previously supplied by either

Colt Colt(s) or COLT may refer to: *Colt (horse), an intact (uncastrated) male horse under four years of age People * Colt (given name) *Colt (surname) Places *Colt, Arkansas, United States *Colt, Louisiana, an unincorporated community, United States ...

Fabrique Nationale de Herstal Fabrique Nationale Herstal (), trading as FN Herstal and often referred to as Fabrique Nationale or simply FN, is a leading firearms manufacturer based in Herstal, Belgium. It is currently the largest exporter of military small arms in Europe. ...

. All rifles were equipped with a fixed A2

stock In finance, stock (also capital stock) consists of all the shares by which ownership of a corporation or company is divided.Longman Business English Dictionary: "stock - ''especially AmE'' one of the shares into which ownership of a company ...

and a

Knight's Armament Company Knight's Armament Company (KAC) is an American firearms and firearms parts manufacturer, best known for producing the Rail Interface System (RIS) and the Rail Adapter System (RAS) grips for firearms use. They currently produce a variety of firea ...

2-stage match grade trigger The upper receivers were flat top style, but unlike the SAM-R and SPR, they did not have extended feed ramps. *Barrel: The 1:7

twist Twist may refer to: In arts and entertainment Film, television, and stage * ''Twist'' (2003 film), a 2003 independent film loosely based on Charles Dickens's novel ''Oliver Twist'' * ''Twist'' (2021 film), a 2021 modern rendition of ''Olive ...

barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, ...

from the M16A2 and A4 were replaced with a

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

Douglas Barrels 1:8 twist, 20-inch barrel, with 12 flutes cut into the barrel to reduce weight. The front sight block was installed with 4 set screws instead of two taper pins. The SDM-R retained the A2-style

flash hider A flash suppressor, also known as a flash guard, flash eliminator, flash hider, or flash cone, is a muzzle device attached to the muzzle of a rifle that reduces its visible signature while firing by cooling or dispersing the burning gases that ...

. *Sights and optics: The issued

optic Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...

was a 4×32

Advanced Combat Optical Gunsight The Advanced Combat Optical Gunsight (ACOG) is a series of prismatic telescopic sights manufactured by Trijicon. The ACOG was originally designed to be used on the M16 rifle and M4 carbine, but Trijicon has also developed ACOG accessories for ot ...

(ACOG) (models TA31F, TA31RCO, TA01, TA01B, or TA01NSN). A Matech Industries 600-meter backup

iron sight Iron sights are a system of physical alignment markers (usually made of metallic material) used as a sighting device to assist the accurate aiming of ranged weapons (such as a firearm, airgun, crossbow or even compound bow), or less commonly as ...

was also used. *Handguard: Daniel Defense DDM4 Rail 12.0 handguard, with an octagonal aluminum collar locking it to the upper receiver. The handguard provides a free-floating

Picatinny rail The Picatinny rail ( or ), or Pic rail for short, also known as a MIL-STD-1913 rail, 1913 rail or STANAG 2324 rail (cancelled), is a military standard rail interface system that provides a mounting platform for firearm accessories. It was o ...

forend. *Bipod: A Harris S-L

bipod A bipod is a V-shaped portable attachment that helps support and steady a device, usually a weapon such as a long gun or a mortar. The term comes from the Latin prefix ''bi-'' and Greek root ''pod'', meaning "two" and "foot" respectively. Bipod ...

attached to an ARMS #32 throw-lever rail mount was mounted to the underside of the handguard. Since the handguard was free-floating, it did not come into contact with the barrel, and any pressure from the bipod on the handguard did not deflect the barrel.

Variants

The

82nd Airborne Division The 82nd Airborne Division is an Airborne forces, airborne infantry division (military), division of the United States Army specializing in Paratrooper, parachute assault operations into denied areasSof, Eric"82nd Airborne Division" ''Spec Ops ...

examined an alternate version, based on the

M4 carbine The M4 carbine (officially Carbine, Caliber 5.56 mm, M4) is a 5.56×45mm NATO, gas-operated, magazine-fed carbine developed in the United States during the 1980s. It is a shortened version of the M16A2 assault rifle. The M4 is extensively ...

. The barrel was to have been an long

fluted Fluting may refer to: *Fluting (architecture) * Fluting (firearms) * Fluting (geology) * Fluting (glacial) *Fluting (paper) Arts, entertainment, and media *Fluting on the Hump ''Fluting on the Hump'' is the first album by avant-garde band Kin ...

Douglas barrel with 1:8 twist. A mid-length gas system was to be used, along with the Daniel Defense M4Rail 9.0 handguard. This effort never went beyond the staffing process.

References

External links