The Brownells bolt lapping tool is a spring-loaded device crafted to provide consistent, linear pressure, ensuring that bolt lugs stay square against the receiver during the lapping process with 600 grit - 800 grit silicon carbide abrasive. This tool offers superior results compared to relying solely on thumb pressure. Furthermore, the interchangeable threaded sleeves are designed to be compatible with popular actions. The M14/M1A sleeve assembly features an oversized diameter plunger and a specialized lapping handle, specifically engineered to meet the unique requirements of these models