M14 EBR

From the Metal Gear Wiki

The M14 EBR is a shorter modernized version of the M14 rifle initially developed in 1957 for the U.S. military. Designed as a replacement infantry rifle for the M1 Garand, the M14 saw a significant amount of use in Vietnam before it was replaced as an infantry rifle by the M16, though it continues to serve as a sniper rifle for other armed forces. The EBR variant has multiple rails that allows it to be customized with multiple accessories. In MGS4, it can be modified three times for distant sniping.