RIFLE: F-1 FIREARMS MODEL FDR-15, SERIAL NUMBER 110-22408, BLACK (MATTE), SEMI - AUTOMATIC, 223 WYLDE, 16" STAINLESS BARREL, USED BUT IN GREAT CONDITION. Notes: F1 Firearms FDR 223 Wylde 16in Black Semi Automatic Modern Sporting Rifle F-1 Firearms Forged Upper/Lower Receiver Set F-1 Firearms 13in M-lock Free Float Handguard This rifle include a .223 Wylde chambered barrel and is safe to shoot both .223 Remington or 5.56mm NATO ammunition. If you are interested in shooting both of these calibers from the same firearm, the .223 Wylde chambered barrel is specifically designed to shoot both .223 Remington and 5.56mm NATO ammunition safely without sacrificing performance.