Dilemma! Load to best shot group or best ES & SD?

[dpete]

I think I have finally found a length and powder charge my Grendel likes. Its an Odin Works BCG/bolt and 18" barrel with their intermediate(yes intermediate, its between mid and rifle length) gas system. I'm shooting the Nosler 123 grain CC and it touches the lands at 1.740 on my bullet comparator. The CBTO length on these loads was 1.725 and powder charges ranged from 27.8 grains of 8208 XBR to 28.2 grains.

My dilemma: is it better to go with the best group which does not have the best ES & SD but still decent, or stick with the best ES & SD and let the group fall into place with the consistent velocities?

27.8
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27.9
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28.0
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28.1
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28.2
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[Klem]

ES and SD in a string of muzzle velocities; the SD is a more precise indicator of how close they all are to the average than extreme spread. Extreme spread only indicates something about two of the four velocities whereas SD takes into account all of them. The more velocities in a string the more the SD will be a more useful metric than ES. Even with only 4 shots in your strings the SD is a more useful metric than ES.

[ricsmall]

Shoot them at distance and pick the most accurate load. I had some 280 AI loads that had single digit SD and ES, but only grouped @2" at 400. I think my best load was 13.5 SD and 27 ES and it shoots 1" or better at 400. Just my $.02

Richard

[JASmith]

At first glance, there doesn't seem to be a lot of difference in group sizes. Try plotting the group size vs charge weight.

Then repeat.

In the end, you want to grab the load that performs best over several range sessions.

Going to longer distances per Richard's suggestion is anexcellent extension of the exercise.

[dpete]

Even with only 4 shots in your strings the SD is a more useful metric than ES.

Despite how a couple of them look, all of the strings were 5 shots. I forgot to mention that the range on these was 100 yards.

[Klem]

To find your best powder/OAL I would stick with 100yds. The reason being is that you want to eliminate wind as much as possible. One less variable to account for in the findings.

I agree with the idea of graphing your data however, so you can interpolate the spot where the group size is smallest.

[ricsmall]

I don't worry about horizontal dispersion unless it's really wide. When I'm finding my node I'm looking for good vertical. This works for me but it's usually not windy enough here to hurt anything at 300 yds. Besides it's good for your practice!! Lol

Richard

[ryeguy]

A load with the best ignition and burn characteristics as measured by velocity ES & SD may not be optimum for your barrel harmonics. If I got those results, I do more work with #1 & #5.