Ultradyne USA Mercury, Comp, 6.5 Creedmoor, Black, Fits 5/8X24Thread UD10717 The Mercury Muzzle Brake has been engineered to precise specifications to provide superior recoil reduction and inhibit muzzle rise with a calibrated release of blast energy. Progressive 90-degree side ports re-direct combusting gases at precise intervals to disperse the recoil impulse for efficient follow-up shots. With an included timing nut" the Mercury can be indexed for optimal performance.