United States Army Squad Designated Marksman Rifle


Soldiers from the 3rd Infantry Division with SDM rifles.
Type Designated marksman rifle
Place of origin United States
Service history
In service 2004–present
Wars Operation Enduring Freedom, Operation Iraqi Freedom
Weight 10 pounds (4.5 kg) with optic & fully loaded 30-round magazine
Length 39.5 inches (1,000 mm)
Barrel length 20 inches (510 mm)

Cartridge 5.56×45mm NATO
Action Gas-operated (direct impingement)
Rate of fire Semi-automatic
Muzzle velocity 3,050 ft/s (930 m/s)
Effective firing range 600 metres (660 yd)
Feed system 20- or 30-round detachable box magazine

The United States Army Squad Designated Marksman Rifle (SDM-R) is a heavily modified M16-series semi-automatic rifle intended to provide increased accuracy at longer ranges, giving infantry squads greater firepower.


The addition of an embedded marksman at the platoon or squad level has been a continuing process in the U.S. military. 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 first and designated marksman second. The SDM is not meant to be a squad sniper who engages the enemy with precision fire at extreme 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 (5.56×45mm NATO caliber) built in-house by the U.S. Army Advanced Marksmanship Unit, and was informally known as "the AMU rifle". SDM-R's have only been built for one major Army division and is not an Army program of record. 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 that led to the development of weapons such as the United States Navy Mark 12 Mod X Special Purpose Rifle (SPR) and the SEAL Recon Rifle.

The National Guard Marksmanship Training Center of the Arkansas Army National Guard 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.[1]

Task Force Small Arms Readiness Group (TF SARG) conducts the week-long SDM course at the SARG academy at Camp Bullis, Texas. Many of the instructors are President's 100 recipients.



The 82nd Airborne Division examined an alternate version, based on the M4 carbine. The barrel was to have been an 18-inch (460 mm) long fluted 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.

See also

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  1. "Squad Designated Marksman Course (SDMC) MTC-005". Marksmanship Training Center. Arkansas Army National Guard. Retrieved 2009-05-22.

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