Having a proper muzzle crowning on your barrel is very important to accuracy. When done properly the barrel is indicated in to less than .0001 centerline and square to the bore. The crown is then cut with a very sharp single point tool and cut with precision to ensure your bullets leave the barrel straight and true. I use a Harding HLV-H tool room lathe for exceptional precision and accuracy. A barrel spider is used on both ends of the barrel in order to dial the barrel in with precision. Cost of barrel crowning varies depending on if other services are done at the same time.