The complete rifleman magazine did a story on the development of the lazzeroni cartridges in the 1999 edition.His 6.5 mm and 7mm cases are based on an improved 404 jeffery case with a head diameter of .544" while the .308,338/375 and 416 cases have a rim/head diameter which is .578" which is .008" smaller than that of the 416 rigby but .034" larger than the 404 jeffery.In effect the lazzeroni case is based on neither the rigby or jefferey case but is much closer to the dimensions of the rigby case.