According to a SOCOM spokesperson ... The system was primarily developed for use with the M4/ M4A1 Carbine and Mk17 SCAR, though it can also serve on the M14, M16, Mk11 or Mk12 rifles.

Socom II: US NAVY Seals PS2 Online Strategy ... Seals: Option 1: Overlook and Defend Preferred Weapons: M4A1 (SD), M16A2 (M203), M63A, SR-25 (SD), M87ELR Have team members defend the hostages ...