The Hornady Lock-N-Load 6mm BR Modified Case is specially engineered for use with Lock-N-Load Precision gauges featuring precise modifications for accurate reloading measurements.Hornady Lock-N-Load 6mm BR Modified Case (SKU: A6MMB)Special fine thread attachment for Lock-N-Load Precision gaugesPerfectly square alignment ensures precise chamber positioningNeck made perfectly round and slightly opened for effortless bullet insertionConcentric design for maximum measurement accuracyEssential for precision reloaders using Hornady gauges to measure cartridge overall length and bullet seating depth for optimal 6mm BR performance.