one grain here or their umm yeah will throw you off lol my rifle loads i will guarentee are never more then maybe a few tenths of grain off from one another at the most 3 tenths of a grain, but 3 tenths wont show any real difference unless you are shooting at ranges like 600 to 1000 yards. load data is written assuming it will be loaded with fl sized brass, in theory neck sized brass loads will have slightly lower pressures which could noticably effect velocity. it was raining today so i didn get out to chrony those fl and ns loads today.