United States Marine Corps Squad Advanced Marksman Rifle

The Squad Advanced Marksman Rifle (SAM-R) was a semi-automatic designated marksman rifle developed and used by the United States Marine Corps. It gave users the capability to provide precision fire in support of a rifle squad, providing precision fire in support of an assault, and aid in observation and adjusting of supporting arms. The SAM-R was retired by the U.S. military in the mid-2010s and thus is no longer in service, having been replaced by the M27 IAR.
Background.
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 Corps Security Force Regiment. 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 M16 rifle 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 were 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), which is located at Camp Lejeune, North Carolina. Squad Advanced Marksmen of I MEF, which is based at Camp Pendleton, California, 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' rifle like the SAM-R used by the Marines of II MEF.
Specifications.
The original test weapon was a modified M16A4 rifle with a free-floated 1:7 stainless steel match grade heavy barrel, a "Mil-Std-1913 modular rail system" (this most likely implies the use of the Knight's Armament Company 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 AN/PVS-22 is preferred.
The later SAM-R was roughly a modified M16A4 pattern rifle:
M38 Designated Marksman Rifle.
After a lengthy period of debate over the role of accuracy "vs." suppressive fire in the Marines, they adopted a new doctrine and weapon in the more accurate M27 Infantry Automatic Rifle for their service rifle in 2018 and it will replace most of the M4 Carbine for the infantry.
Certain M27s are selected for accuracy; when provided with scopes and suppressors they are designated as the: M38 Designated Marksman Rifle, and distributed one per squad.