The Squad Advanced Marksman Rifle (SAM-R) gives U.S. Marines the capability to provide precision fire in support of the rifle squad, providing precision fire in support of an assault, and aid in observation and adjusting of supporting arms.
The Squad Advanced Marksman and his weapon, the Squad Advanced Marksman Rifle was the product of extensive experimentation by the Marine Corps Warfighting Laboratory (MCWL) of the addition of a designated marksman to a Marine squad. The concept of a designated marksman was already in use by the 4th Marine Expeditionary Brigade (Anti-Terrorism) and Marine Security Forces. In exercises, a Marine with a scoped rifle and additional training provided immense benefit to small units. An optic provides information-gathering abilities as well as aiding aiming of support weapons such as machine guns and mortars.
The armorers at the MCWL decided to use the AR-15/M16 pattern in order to maintain a certain level of commonality in both weapon and ammunition. There was some talk of adopting a weapon such along the same lines as the Mk 11 Mod 0, but instead that transferred over to a possible replacement for USMC personnel now using the Designated Marksman Rifle (DMR), a variant of the M14.
The SAM-Rs are assembled by the Precision Weapons Section of the Weapons Training Battalion at Marine Corps Base Quantico. For the War on Terrorism, the approximately 100 assembled SAM-Rs were sent to the 22nd, 24th, and 26th Marine Expeditionary Units (MEU) of II Marine Expeditionary Force (MEF), who are located on the East Coast. Squad Advanced Marksmen of I MEF, which is based on the West Coast, made do with M16A4s with KAC M5 RAS forearms and TA31F ACOGs. They were nicknamed "West Coast SAM-Rs" though they are simply M16A4s with optics and bipods, and not an 'accurized' platform like the SAM-R used by the Marines of II MEF.
The original test weapon was a modified M16A2 rifle with a free floated 1:7 stainless steel match heavy barrel, a "M1913 modular rail system" (this most likely implies the use of the Knight's Armament Company M4 Match/Sniper Free-Floating Rail Adapter System) and an M16A1 trigger assembly (semi and full-auto functioning). A number of day optics were used initially, which included Hensoldt Blitz, Leupold CQ/T, ACOG, Leupold TS-30A1 and ultimately the Leupold TS-30A2. The test night optic was the AN/PVS-17B, apparently now being fielded with USMC combat units though the PVS-22 is preferred.
The currently used SAM-R is roughly a modified M16A3 pattern rifle: