Hi everyone. I did some load testing for my .308 this weekend and have a couple questions for you long range shooters. I was using my chrono and had speeds from 2590-2625. Is this a normal spread? I guess I shot 5 rounds through it with chrono 10 feet from muzzle. Also, at 500-600 yards, how would these deviations affect point of impact? I weigh each charge of H4895 (41 grains) and am using a Hornady 168 grain Amax and CCI primer. Each charge is weighed on rcbs 505 scale. I plan on having a rcbs chargemaster before Christmas. Any advice or are these normal differences? Thanks
Velocity Deviation - .308
- Thread starter hvychev77
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USSR
Member
When I was shooting in 1,000 yard competition, we always looked for loads that produced ES numbers of <= 20 and SD numbers of <= 5.
Don
Don
USSR
Member
ES = Extreme Spred, and SD = Standard Deviation.
Don
Don
ironworkerwill
Member
An ES of 35fps is not terrible. At 500 yds wind will play a much bigger role.
You can plug all your data in at JBMballistics.com and get approximate vertical dispersion by running high and low.
Example: ES of 30fps = +- 5'' vertical dispersion @ 1000yds( .284@ 3000fps w/ 168gr VLD)
http://www.gunwerks.com/Long-Range-University/Learning-Articles/Powders,-Primers,-and-Long-Range-Shooting
BillB204
Member
Extreme spread is the difference between your highest and lowest readings. The group you described had a 35 ES. This isn't bad. But you need to try to get it down to 15-20. And the longer your shots, the more effect ES can have on POI. A few things may help get your ES down. Try match grade primers, magnum primers, and magnum match primers. Try more or less bullet jump. Try different kinds of sizing - full length, full neck only, partial neck only.
Reloading - the never ending search for perfection!
Reloading - the never ending search for perfection!
Weighing out charges helps but does not guarantee small ES.
Small ES is achieved by voodoo. Some loads have it. Most do not, even though each powder charge is exactly the same and each case weighs the same, and each bullet is just like the other, and the weather is nice.
The joys of load development.
And just because you have an ES of 10 does not mean your group is gonna be tight.
So then you have to balance accuracy with ES. Do you want a MOA load with a small ES or a half MOA load with a moderate ES.
Small ES is achieved by voodoo. Some loads have it. Most do not, even though each powder charge is exactly the same and each case weighs the same, and each bullet is just like the other, and the weather is nice.
The joys of load development.
And just because you have an ES of 10 does not mean your group is gonna be tight.
So then you have to balance accuracy with ES. Do you want a MOA load with a small ES or a half MOA load with a moderate ES.
spitballer
Member
I don't shoot long rang like some of these guys, but from what I understand the big challenge is going to be staying ahead of a destabilizing shock wave out to the range you've chosen. At longer ranges this may necessitate using heavier projectile, even though that heavier projectile may actually start out slower.
Thanks guys. So far up to 300 yards, my loads have been accurate. Last sunday I shot a 3 shot group at 303 yards that was 2.01". I'm pleased with that since the wind was kicking around pretty good. I'm sure I'm not perfect with my form either. So, I'm still making my charts at specific ranges, what my turret adjustments are, and will continue to work my way out and just general research on proper form and such. Thanks for the help!! Cheers
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