The Spikes Tactical ST5BG01 Bolt Carrier Group is a rugged, high-performance AR-15/M16 BCG engineered for reliability in 223 Rem and 5.56x45mm NATO platforms, finished in a durable Black Phosphate on steel for enduring corrosion resistance and smooth cycling. This HPT/MPI bolt assembly delivers enhanced headspace integrity and consistent lockup under demanding conditions, making it an ideal choice for rifles that demand precision, durability, and repeatable performance. Designed to work seamlessly with standard and Build-to-Performance configurations, the ST5BG01 features a robust M16-style bolt that supports reliable chambering and cycling across a wide range of loads, while the phosphate finish reduces wear and ease of maintenance in the field. Spikes Tactical combines tight manufacturing tolerances with proven reliability to deliver a bolt carrier group that supports steady, repeatable operation in tactical, sport, and training scenarios. Whether you're upgrading an existing AR-15 or assembling a high-performance rifle, the ST5BG01 provides a proven platform for consistent extraction, reliable bolt function, and smooth cycling, helping you maximize accuracy, shorten follow-up times, and maintain confidence in critical shooting situations.