sorting your brass by weight, can that make a big difference? if so what is your method?

I don't know if it makes much difference but I full length resize, trim and chamfer, ream the primer pockets then deburr and chamfer flash holes.

Then I weigh and sort my varmint and target brass individually (long and tedious process).

I usually just set aside the extremely high and low variations.

It's probably has the least affect. If you sort by brand it's probably just as beneficial.

What you're really doing in weight sorting your brass is determining the interior volume of your cases. For hunting loads and hunting accuracy you need a variance of at least 10g in the larger sized cases to make much difference. In the smaller cases like 308 and smaller, 5g or even less, can make some difference.

In a 338 Win Mag I've done quite a bit to determine what effect, if any, weight differences make. I've found that a weight difference in a dry case of 17g, has the same effect as adding or subracting one grain of propellant. Extrapolate from that and you'll see that even a 4 or 5g difference in a larger case won't have much effect.

Having said that, I sort all my cases to within 1.5% of dry weight. I do believe it makes a difference, at least to my confidence and peace of mind, and it eliminates an additional factor when developing loads.