Replacement bolt for any of our rifles chambered in 6.8mm, including both the Six8 and legacy M6 platforms as well as the .224 Valkyrie. This bolt fits into any Mil-STD bolt carrier and functions accordingly. Our Advanced Combat Bolt is an evolution in bolt design. With a fully supported bolt face, our ACBs lack the two undercuts on either side of the extractor pocket that weaken traditional bolts. In addition, the extractor utilizes a dual-spring design that increases extraction force and triples the service life. Machined out of a super-alloy formulated to take extreme loads without failure, our ACBs are also shot-peened for extra durability. A nickel-boron coating increases strength and lowers the coefficient of friction. All of these factors and more make our Six8 ACB the best choice for any 6.8mm SPC firearm.