Finding ideal powder charge (.284win)

[UndFrm]

I got a used rifle with 1500 or so rounds on it. I wanted to figure out the load for the components I have and this is what I did:

Loaded some rounds with 0.3gr increment (1 for each) and chronoed it while looking at the vertical dispersion. What I got is this:

The vertical dispersion for these looks acceptable but the velocities aren't ideal.
Where the velocities are ideal, the vertical dispersion isn't great.

Components:
Lapua 6.5 284 necked to 7mm
CCI 200
4831sc
32" barrel

I haven't looked at the seating depth at all, that will be my next step once I figure out what powder charge to test with.

Based on the attached images, is there a charge I should go with, test further with? I am unsure if I should be looking at the vertical dispersion only or the consistent velocity only for 2 or 3 charges. The 2 aren't consistent for 2 or 3 charges, only 1 or the other.


Thank you

 

[RegionRat]

When something looks unstable between two steps, you either avoid it or repeat the test to see if it was real.

If I understand your captions, the step when you went from 51.2 to 52.1 was a significant jump. (Where was 51.5 to 51.9?) The remaining steps are smooth with no obvious advantage, but most importantly no big jumps.

In this type of testing, you have no way to judge velocity stats, so you just note the speeds and study the targets. Any so called "flat spots" in the velocity plots of low sample ladders are an illusion that evaporates when you shoot more samples.

Then, you would have to have on the order of 7 or more shots per step just to have a preview of the ES/SD potential of the recipe.

In follow up testing, the additional samples you will shoot at any given charge will give you a preview of the velocity issues.

So with that said, you can either shoot the whole ladder again at a longer distance to see if there really is a vertical node or evidence of a compensation advantage, or just pick something in the higher end and add samples to test for group size and POI stability.

If we stand on these results, we would avoid 51.2 to 52.1. We would go test groups of at least three shots in 0.1 or 0.2 grain steps from 52.1 to your pressure max. We would find the middle of the best stable region in that series, and test again to see if the results are stable in different weather on different days.

As an option, if you can seat at the range, you can test seating depth in the middle of the charge range you tend to like. Take a decent sized batch of your best charge that is loaded long to the point of light jam, and then gradually seat them deeper while observing the target. Go ahead and overshoot the steps you think look good, and then go back and see if that repeats. YMMV

Good Luck and in for the range reports.