No, one bullet is not larger in diameter than the other. They should both have a MAXIMUM diameter of .284, but depending on the ogive of the bullet, one will reach that diameter at a different point from the nose of the bullet, and will be .284" in diameter for a different length of the bullet. A .284" bullet should touch the lands where the bullet is actually .276" (I think, if the lands are .004'' deep). A .308" bullet will touch the lands where the bullet is .300" in diameter, and so on. The reason for the differences is that the deep part of the rifling of a 7mm rifle should be .284", and with .004" deep rifling, you have a total of .008", which makes the distance across the lands .276."