The E4 / ETB Bolt Assembly from Centurion Arms is engineered to raise the reliability and service life of your bolt carrier group. Dual ejectors deliver more consistent ejection, a feature that proves especially important for suppressed firearms where ejection dynamics change. Centurion redesigned the lug-to-body radius to add material where lugs most often fail, significantly reducing the risk of lug shear under high round counts.
Built to exacting standards, the bolt is hard-chrome plated, shot-peened, and magnetic-particle inspected (MPI) to ensure longevity and toughness. It accepts standard extractors (with black inserts) and standard gas rings for easy logistics, while offering the option of Centurion’s upgraded 5-coil chrome-silica stress-relieved extractor spring (EXT-SPRING) or Colt OEM springs. Although the E4 bolt supports standard cam and firing pins, it is NOT compatible with KAC’s proprietary E3 cam/firing pins.
Buy the Centurion Arms E4/ETB Bolt Assembly at Dirty Bird USA for a durable, suppression-friendly bolt solution.



