These barrels start as a 3 pound bar of certified pure T-416 steel and are cut to precise standards before being heat treated and sub-zero frozen for maximum strength and stress relief. Barrels are rifled with 1 in 16" left hand twist. This deep cut, broached rifling gives superior accuracy with all types of bullets, including cast lead. The dimensions are cut to the maximum tolerances on the outside of the barrel which means less fitting work and more accuracy. Drop-in barrel bushing, barrel link and link pin are included (except Bull Barrels). Requires installation by qualified gunsmith. Bushing, Link and Link Pin are included except Bull Barrels.