| US Army SDM-R | |
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 A pair of soldiers from the 3rd Infantry Division with SDM rifles. |
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| Type | Sniper rifle/designated marksman rifle |
| Place of origin |  United States |
| Service history | |
| In service | 2004–present |
| Wars | Operation Enduring Freedom, Operation Iraqi Freedom |
| Specifications | |
| Weight | 10 lb. (Fully loaded, w/ Heavy Barrel, Optic & 30 Rounds) |
| Length | 39.5 Inches |
| Barrel length | 20 Inches |
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| Cartridge | 5.56x45mm NATO |
| Action | Gas-operated, Rotating Bolt |
| Rate of fire | Semi-automatic |
| Muzzle velocity | 3,050 ft/s (930 m/s) |
| Effective range | 600 yards (550 m) |
| 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 rifle that provides increased accuracy over range, giving infantry squads greater firepower.
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Background
The desire to have an embedded marksman at the platoon or squad level seems to be something appearing across the board in the U.S. military. The United States Marine Corps (USMC) experimented heavily with this during Project Metropolis, before creating the Squad Advanced Marksman position and creating a rifle specifically for them. The U.S. Army has 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 Squad Designated Marksman is an integral part of the squad and serves as rifleman first and designated marksman second. The SDM is not meant to be a squad sniper that engages with precision fire at extreme ranges. Instead, the soldier is trained to directly support the squad with well-aimed shots at ranges slightly beyond the normal engagement distances for riflemen. Much like the USMC's Squad Advanced Marksman Rifle (SAM-R), the SDM-R is an accurized AR-15/M16-type rifle (5.56x45mm NATO caliber) built in-house by the U.S. Army Marksmanship Unit (USAMU; this rifle is also known informally as "the AMU rifle"). SDM-R's have only been built for one major Army division and is not a 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 like the Mk 12 Mod 0/1 and the SEAL's Recon Rifle. Similar needs have also been identified by the USMC, which led to a similar development to the SDM-R in the USMC SAM-R.
Specifications
- Upper and lower receivers: from most reports the rifles appear to have been built up using existing lower receivers in inventory. What this means is the rifles are completed using A2/A4 lower receivers previously supplied by either Colt or Fabrique Nationale, with a fixed A2 stock. The upper receivers are flat-top style. Unlike the SAM-R and SPR, it does not have extended feed ramps. The trigger has been replaced with a Knight's Armament Company 2-stage match grade trigger capable of only semi-automatic fire.
- Barrel: the traditional 1:7 twist, 20-inch barrel has been replaced with a stainless steel Douglas 1:8 twist, 20-inch barrel, with 12 flutes cut into the barrel to reduce weight. The front sight block is installed with 4 set screws instead of two taper pins. The A2-style flash hider is retained.
- Sights and optics: the issued optic is a 4x32 ACOG (TA31F, TA01, TA01B, or TA01NSN). A Matech Industries 600-meter backup iron sight is also used.
- Handguard: the SDM-R uses a Daniel Defense M4Rail 12.0 handguard, with an octagonal steel collar locking it to the receiver block. The Daniel Defense handguard provides a free-floating MIL-STD-1913 rail forend.
- Bipod: a Harris S-L bipod on ARMS #17 throw rail mount is mounted to the underside of the handguard. Since the handguard is free-floating, it does not come into contact with the barrel, and any pressure from the bipod on the handguard will not deflect the barrel.
Variants
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 beyound the staffing process.
Photos
 Soldiers from the 3rd Infantry Division with SDM rifles, using TA31F ACOG sights. The rifle on the right has an AN/PEQ-2 illuminator with the tape switch attached to the magwell. |
 The soldier on the left has a painted SDM rifle with a TA01NSN ACOG sight. |
See also
- U.S. Marine Corps Squad Advanced Marksman Rifle
- U.S. Marine Corps Designated Marksman Rifle
- SEAL Recon Rifle
- United States Navy Mark 12 Mod X Special Purpose Rifle
- List of individual weapons of the U.S. Armed Forces
- Designated marksman
External links
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AR-10 • AR-15 • M16/A1/A2/A3/A4 • M4/A1 Carbine • Diemaco C7, C8 • Colt Commando, XM177, CAR-15 • Colt 9mm SMG • Bushmaster M4 • HK416 • HK417 • M468 • M231 FPW • SDM-R • SAM-R • Mark 11 'SWS' / SR-25 • M110 SASS • Mark 12 'SPR' • SEAL Recon Rifle • Mark 18 'CQBR' • Ares Shrike • La France M16K • SR-47 • Colt Automatic Rifle / CAR |
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