This is a SilencerCo Brake known as the Bravo, model AC2081.
Replace the Front Cap on your Omega 300 or Hybrid 46 with a SilencerCo Bravo Anchor Brake. The Anchor brake improves sound reduction and mitigates recoil" allowing the shooter to re-acquire the target for faster follow-up shots. Bravo accessories are compatible with Omega 300" Hybrid 46" and Harvester 338.
Features:
Improves sound reduction
Reduces recoil
