You’ll need a chrono to see the difference. You’ll need to have been using it awhile to have enough control over your velocity spread to notice a difference from weight sorting brass. I did anyway. Weighing and filling a few cases to see the correlation between case weight and volume is a worthwhile learning experience too. It’s not 1:1 and by the time you’re down to 2 grains of brass variance you’ve pretty much beaten it to death. Another problem is the lower water density and its surface tension effects really work against the sensitivity of the test. Try it and you’ll see the problem.
As far as doing this with groups, I’ll save you some time and say don’t bother at less than 6-800 yards. My last 6.5CM ladder had a velocity range of 100 fps for 1.8 grains of powder and had a total vertical spread of ~3/4 moa at 400 yards.
Let’s say we’ve controlled the velocity spread due to differences in brass internal volume to 8 fps by sorting and it was 3x that, or 24 fps, without sorting. That probably overstates the effect of breaking it into three 2 grain lots by a little, but it also ignores the culls which really screw things up.
If your ES is 60 fps, the contribution of things other than brass volume is (X^2+24^2)^1/2= 60, X = 55 fps variation from other things. If we drop the 24 fps down to 8 fps, the new expected ES is going to be (55^2+8^2)^2 = 55.6 fps. With 10 shot samples, it’s going to be hard to catch the difference between 60 fps and 56 fps. This is the don’t waste your time group. They shoot lots of good groups, “if they do their part”. This is a large group and I’m not disparaging it in any way.
If your ES is 30 fps, the contribution of things other than brass volume is (X^2+24^2)^1/2= 30 fps, X = 18 fps variation from other things. If we drop the 24 fps down to 8 fps, the new expected ES is going to be (18^2+8^2)^1/2= 19.7 fps. You’ll probably be able to consistently see the difference between 30 and 20. On the chrono anyway.
So why do it? I’m not loading for 400 yards. If I’m stuck developing long range loads at 100 yards, just going through the same hole isn’t nearly good enough, they all have to be going through that hole at the same speed. I am more likely to get more of them to go through that hole, but it would take a lot of shooting to prove it. Using a 175 SMK at 2650 fps, every 30 fps change in velocity gives a vertical impact shift of 12” at 1000 yards, so the difference between 30 fps and 60 fps ES is huge. That doesn’t include barrel timing effects which can be almost as large. If you control your velocities to 30 fps, you have a fighting chance of finding and parking yourself in the middle of an accuracy node. 60 fps, it’s not as likely. Case weighing won’t drop your ES 30 fps, but its part of playing in the 30 fps ES league.
The next part is how much time or money we invest. I already own the digital scale and case bins, so no additional cost there. I put 3 bins in front of me and sort into 2 grain lots, throwing the high and low culls to either side. I can sort about 15 cases a minute using a digital scale. This has about the same effect as switching from dropped to trickled charges, which has to be done for every loading and I sure the hell can’t trickle 15 cases a minute. So if you’re trickling, weight sorting is a good idea. If you’re not, you may not be doing enough to notice any improvement.
Another issue is where the brass came from. My 308 and 223 comes from local LE. If you bought 100 new Lapua cases, the benefits are going to be a lot lower than what I’m discussing here.
Whether or not to do it depends on what you’re trying to accomplish. And yes, the group that doesn’t need to do it is much larger than the group that does.
