This replacement bolt for any of LWRC rifles chambered in 6.8mm, including both the Six8 line and the legacy M6 rifles with 6.8 SPC barrels. This bolt fits into any Mil-STD carrier and functions accordingly. With a fully supported bolt face, LWCR's 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, they 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.