Question on ES and SD with powders

[Scott E Ames]

I am starting on loads for 2 new rifles and have decided to use the ladder test method. I have read up on this but my question on choosing a specific powder to use is " Does the powder which has the best ES/SD show that characteristic across the range of charges from to low to max or will it fluctuate just like group size and powder charge or group size and seating depth?"
Thanks for your observations.

 

[Dmagna]

Sometimes it does and sometimes it doesn't. I have had an SD of 30 on a 5 shot group and my next powder charge with an increase of .3 gr will give me a 5 SD. Sometimes my loads no matter the charge will have 5 shot groups with an sd of less 10 and tiny groups. My 6mm creed did this to me, actually made it very hard to find a load because each test charge had a good SD and ES. So then I went to a seating depth test on the 3 fastest loads and found a good load from there.

 

[Scott E Ames]

Looks like this is a dead subject!!!!!!!!!!

 

[Tiny Tim]

As Dmagna said, It can go either way. "My experience" has been that at either end of the loading spectrum (starting and max loads), they may vary more from charge weight to charge weight tested. At the low end, pressures may not be high enough to get a consistent burn with some powders, and at the high end, you may approach "pressure spikes" that contribute to the wide ES/SD. A full ladder and seating depth load workup will generally give you the best load for the bullet/powder combo you have selected.