About the BCM® Standard 14.5″ M4 (SOCOM) Complete Upper Receiver
The SOCOM M4 profile is a mid-weight profile barrel for the M4A1 Carbine. The flats milled under the handguards are for mounting of the M203. SOCOM requested the mid profile to better handle the volume of fire from their shooters. This profile is being adopted as a new standard for the M4A1 Carbine.
