A 2008 United States militarymarket survey for a Precision Sniper Rifle called for 1 minute of arc extreme vertical spread for all shots in a 5-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters. In 2009 a United States Special Operations Command market survey called for 1 MOA extreme vertical spread for all shots in a 10-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters. The 2009 Precision Sniper Rifle requirements stated that the PSR when fired without suppressor should provide a confidence factor of 80% that the weapon and ammunition combination is capable of holding 1 MOA extreme vertical spread, calculated from 150 ten round groups fired unsuppressed. No individual group to exceed 1.5 MOA extreme vertical spread. All accuracy taken at the 1,500 meter point. Other requirements were that the rifle weigh less than 18 pounds loaded, have Picatinny rails, and have an easily changeable barrel.
Tender criteria
Sniper Rifle requirements included:
The system shall be chambered to safely fire factory produced "non-wildcat" Small Arms Ammunition Manufacturing Institute or Commercial European standard ammunition.
With primary day optic and ammunition the system shall provide 1.0 MOA from 300 to 1500 meters when fired from the shoulder or an accuracy fixture in nominal conditions.
This is further defined as 1 MOA Extreme Vertical Spread for all shots in a 10 round group at the stated distances.
Mean Rounds Between Failures shall be 1000 rounds.
The system shall have an overall length no greater than 52" in full configuration / extended excluding suppressor with a single component no greater in length than 40".
The system shall weigh no more than 18 lbs with a 12:00 MilStd 1913 rail and a loaded magazine with 5 rounds.
The system shall be capable of operator breakdown into major components in less than two minutes.
The system will assemble from the major component breakdown in less than two minutes by the operator.
The system will assemble from breakdown with no change in weapon zero.
The system will have an integral MilStd 1913 rail at the 12:00 position, the rail will be capable of maintaining bore sight alignment and weapon zero while conducting routine firing combined with combat movement and operational training drills.
On March 8, 2013, Remington announced that the Modular Sniper Rifle had won the contract, beating out the Sako TRG M10. The contract is worth US$79.7 million for 5,150 rifles including suppressors, and 4,696,800 rounds of ammunition over the following ten years.
Re-compete
However, in 2018 decided that the Mk 21 did not conform to SOCOM requirements at the time, and the program was re-competed with the Barrett MRAD selected in 2019 as the Mk 22 Advanced Sniper Rifle solution.