PROOF Research pre-fit carbon fiber & steel barrels for the Impact Precision 737R, 787R, and NBK/777R are to be installed in a simple operation requiring few specialized tools. These barrels come chambered and threaded for an easy install - torque on, ensure headspace with proper gauges and head to the range! Shot for shot accuracy and performance - there is simply no better choice for the Impact Precision actions than our carbon fiber & steel pre-fit barrels.