69g SMK and H322

[AFshirt]

I finally got a chronograph going and wanted to test the 69g SMKs I have been using. For my meager skill I was decently impressed.

I am using Markm's suggested load of 22.9g of H322 and a Wolf magnum SRM primer.
mixed LC brass
2.25 OAL
Blackhole Weaponry 18inch barrel

I fired 10 shots through the crono and got
an average velocity of 2703
Standard deviation of 34
extreme spread of 98

I then fired the remaining 5 I had loaded for testing up at 100yards using a SWFA 12x scope.

I fired the first 4 then adjusted the scope for the 5th. 100yd groups are great now I just need to figure out how to get the SDs and ESs down to start pushing the load out to longer ranges. I'll take any suggestions to drop that SD down. For comparison, I fired 10 rounds of ADI 168g SMKs though my bolt action and got a SD of 8 so I know single digit deviations are possible.

[Auto-X Fil]

Don't expect .308 SD's from 223. The case is half the size, so variations in charge weight or case volume will have 2x the effect on SD. To get very consistent velocities:

Sort cases by weight to get similar volumes (especially whe using mixed LC brass)

Measure the powder more precisely (+/- 0.1gr should give +/- 12-15fps)

Use primer/powder combos that get along.

Use temp-consistent powders.


In general, SD in the teens for .223 is quite good. 25fps will only cause 2" of vertical at 600yd, so it's not worth trying to get super-low SDs unless you're shooting F/TR in a bolt gun with 90's or something.

[markm]

SDs will drive you nuts. I'll get great ones some days and wild ones other days with the same formula. What chrono are you using? If it's not a really nice one, there can be a little bit of accuracy wiggle.

If I was getting the groups you are before the optic adjustment, I'd just roll with it.

[AFshirt]

It is a Prochrono, I've been told that the lower your SD the more consistent your prep work. This is going to be my baseline. Next test is going to be sorted cases deburred flash holes etc. then if the SDs don't show the effort worth it then so be it

[markm]

Sorting cases in .223 has never helped my numbers.... and deburring flash holes is total insanity in my opinion.