CREATE TABLE table_23431 ("Colt model no." TEXT, "Military designation" TEXT, "Barrel Length" TEXT, "Barrel" TEXT, "Handguard type" TEXT, "Buttstock type" TEXT, "Pistol grip type" TEXT, "Lower receiver type" TEXT, "Upper receiver type" TEXT, "Rear sight type" TEXT, "Front sight type" TEXT, "Muzzle device" TEXT, "Forward assist?" TEXT, "Case deflector?" TEXT, "Bayonet lug?" TEXT, "Trigger pack" TEXT)

Which muzzle devices are on the Colt 603?
SELECT "Muzzle device" FROM table_23431 WHERE "Colt model no." = '603'
SELECT "Muzzle device" FROM "table_23431" WHERE "Colt model no." = '603'