The Angstadt Arms UDP-556 is a semi-automatic AR-15 rifle chambered in 5.56 NATO/.223 Remington. It is designed to meet the needs of demanding users in all conditions and applications, from sports shooting, target practice, and home defense to complex tactical applications. The UDP-556 has all the AR-15 features anyone can expect from a modern AR-15 rifle. It features a 16" chrome-moly barrel, a muzzle threaded to 1/2x24 for attaching a wide range of aftermarket muzzle devices, a B5 Systems SOPMOD stock, a B5 Type-23 pistol grip for ergonomics and a confident shooting experience, and an ultra-light free-floating handguard with M-LOK attaching slots. The rifle uses a standard AR-15 magazine and is compatible with standard aftermarket AR-15 magazines. The available finish is Cerakote in various colors and all the main components have been anodized for longevity and wear resistance during heavy-duty use in harsh environments.