That 1.0 grain extreme spread is very, very good.
A fun experiment to try, if you bother weighing and sorting your brass:
- set aside your very lightest one or two cases, and your very heaviest one or two cases. Mark "L" on the lighest ones, and "H" on the heaviest ones, and keep them separate.
- sort your brass according to whatever your original plan was, make the very best ammo you can with it. At the same time, also load your "L" and your "H" cases with the exact same loading. Put them in your ammo box upside down so that you won't accidentally shoot them, or put them in a box of their own.
- the next time you are shooting a match, at the longest range you ever shoot, immediately after you finish shooting the match (if time allows), fire your "L" and your "H" ammo. You are doing this with a fully-sighted in rifle at this point, which has just fired a group that you've plotted and you understand.
- carefully record where the "L" and the "H" ammo strikes the target.
From this, you will be able to determine how sensitive your ammo is to case weight variations. If your "L" and "H" ammo go into the same group that you shot with your weight-sorted ammo, this tells you that you might not have to really sweat the details of the brass sorting. Or, perhaps that 1-grain "bins" for your sorting is as fine as you need to go (I've seen some people sort to 0.1 grain "bins"; I don't think that this is necessary, but you can figure this out with your own testing).
This technique of shooting "outliers" and see whether or not they go into your group, can also be used for learning the effects of:
- the heaviest or lightest bullet you find in a box
- a carefully made piece of ammo with 0.5 grains more or less powder
- A damaged bullet (e.g. an unusually blunt or sharp tip)
- etc
I sort them into 1 gr batches and go from there.
