Horizontal in load development

Joined
Dec 24, 2020
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24
Location
grease county
So 308 175mk 41-42 grs of imr 4064, coal 2.800. At 500 yards the vertical is 1-1/4 inch spread, that's the best node, but my horizontal is 3-4 inches. So I'm still doing load development, but I'm wondering will shortening coal help horizontal dispersion? I can't go longer due to mag length. Also what's a good increment to decrease at a time?
 

Jud96

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Jun 30, 2013
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3,020
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Michigan
Wind would be my first guess. I would either retest on a calm day or shoot groups at 100 yards. Your seating depth can be adjusted to change your group size and shape. Contrary to popular belief, seating bullets both closer and further from the lands can both negatively or positively affect your group sizes. I would suggest working forward in .005 increments until you reach your lands or your magazine restricts you or until you find a good load. If you don’t get better results, then work back from 2.800” and see if that improves things. Be careful and don’t seat the bullets too deep into the cases.
 
Joined
Dec 24, 2020
Messages
24
Location
grease county
Wind would be my first guess. I would either retest on a calm day or shoot groups at 100 yards. Your seating depth can be adjusted to change your group size and shape. Contrary to popular belief, seating bullets both closer and further from the lands can both negatively or positively affect your group sizes. I would suggest working forward in .005 increments until you reach your lands or your magazine restricts you or until you find a good load. If you don’t get better results, then work back from 2.800” and see if that improves things. Be careful and don’t seat the bullets too deep into the cases.

The longest I can go is 2.800, because I do want to use the box mag, what increments should I work backwards?

I will admit there was a slight wind, although I didn't think it was a factor because it was light, maybe not lol
 

Mikecr

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Aug 10, 2003
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5,595
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NC, oceanfront
The best you can do is Berger's recommended full seating testing.
Be sure to back away from your current load so that you can see results of seating instead of simple loss of powder node.
 

338 dude

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Mar 1, 2016
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Tn
The longest I can go is 2.800, because I do want to use the box mag, what increments should I work backwards?

I will admit there was a slight wind, although I didn't think it was a factor because it was light, maybe not lol
.010 is a coarse test or .003 for a fine test when you are getting close
 

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