The M4A1 SD is a suppressed variant of the M4A1 featured in SOCOM: U.S. Navy SEALs and SOCOM II: US Navy SEALs. It is the fireteam's default weapon in most missions. Beginning with SOCOM 3: US Navy SEALs, the games featured the ability to customize base weapons with various attachments including scopes, suppressors, and grenade launchers. As a result, purpose-dedicated variants of weapons such as the M4A1 SD were rendered redundant and excluded.