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Brian Enos's Forums... Maku mozo!

Extreme Spread & Standard Deviation ?


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The lower the Standard Deviation the more consistent your loads are performing.

Where it comes into play is assisting you in selecting loads to make a certain power factor.

From information gleened from other sources on the forum, to assure 99%+ of your loads make major, you would want the velocity of your load to be 3 SD's higher than the minimum needed to make your power factor.

For a major load that uses 165 grain bullets you need a velocity of 1000 fps. If your chronograph indicates you have a SD of 10 fps, you would want to consider loads where the velocity is 1000 fps plus 3 times the SD of 10 for a velocity of 1030.

If your loads have a SD of 30 fps, you may need to load up at 1090 fps to be confident.

So a load with a low SD can be loaded closer to the 165 PF than a load with a high SD, and still be confident it will make major.

Bill

edited because I can't type when I'm sleepy. Good night.

Edited by Flatland Shooter
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