sentences:  Furthermore, as this is a beltless cartridge headspacing is designed to take place on the shoulder, which is considered beneficial by some as it is thought to promote accuracy and prolong case life of the cartridge.As modern belted magnums such as 7mm Remington Magnum and .300 Winchester Magnum actually headspace on the shoulder despite retaining the belt found on their parent cartridge, belted or unbelted is basically irrelevant in discussions of modern cartridges, and particularly so in discussions of unbelted cartridges.SAAMI recommends that the barrel have a 6 groove contour with a twist rate of one revolution in .