The Defender M5 features HM Defense's patented HMB bolt and Monobloc barrel. The Monobloc barrel features an integrally machined gas block, eliminating the need for installation or alignment while ensuring the block will never loosen or fail. The HMB bolt features a reinforced design that removes cam pin hole replaces it with a cam pin socket and tapered cam pin design. This new deign eliminates the natural weak point of mil-spec bolts by significantly increasing metal strength at the cam pin location.