High Quality Content by WIKIPEDIA articles! The M39 Enhanced Marksman Rifle (EMR, NSN 1005-01-553-5196; more formally the Rifle, 7.62 MM, M39 Enhanced Marksman Rifle (EMR)) is a semi-automatic, gas-operated rifle chambered for the 7.62x51mm NATO cartridge. It is a modified and accurized version of the M14 rifle built and utilized solely by the United States Marine Corps (USMC). It is based on the current United States Marine Corps Designated Marksman Rifle (DMR), which it replaced.