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How do you lower S.D.?

 
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  #8  
Old 02-02-2008, 11:45 PM
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I wasn't sure if you were refering to standard deveation in velocity or distance from aim point (should have guessed that you were talking about velocity though). I agree with the above posts that you should let the gun cool between shots. Also, I have noticed a significant difference in velocities from a bad batch of primers. I had about 25 cases primed with some mag primers and decided to fire the primers and resize the cases inorder to use those brass for a test using CCI BR2 primers in my mag. I fired the brass into a bundle of old ripped bluejeans. I was shocked to hear the poof on some and a bang on others and a crack on some. I guess my primers were old and exposed to some bad stuff. I had been disgusted with the results of my chrono tests last summer using that load and I think I know why the SD was so large now!

I am only going to use fresh primers from now on.
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  #9  
Old 02-03-2008, 12:18 AM
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What kind of scope,rings and bases do you have. Did you mount the scope yourself. Have you been able to shoot consistant sub-moa groups with other rifles that is as raunchy as this one. Some of the little skinny barreled sporters need some work on the rifle itself. I wished i had a dime for every dollar i had spent trying to find what is causing a rifle not to shoot as well as it should. Ammo can cause some of it but I would just about bet your problem is in your set-up somewhere. Many of the rings and bases are just not up to the task of keeping everything pointed in the right direction on any rifle let alone one like yours. Everything has got to be tied down.
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  #10  
Old 02-03-2008, 08:58 AM
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Quote:
Originally Posted by Augustus View Post
What kind of scope,rings and bases do you have. Did you mount the scope yourself. Have you been able to shoot consistant sub-moa groups with other rifles that is as raunchy as this one. Some of the little skinny barreled sporters need some work on the rifle itself. I wished i had a dime for every dollar i had spent trying to find what is causing a rifle not to shoot as well as it should. Ammo can cause some of it but I would just about bet your problem is in your set-up somewhere. Many of the rings and bases are just not up to the task of keeping everything pointed in the right direction on any rifle let alone one like yours. Everything has got to be tied down.
What does the rings and bases have to do with S.D.?:confused:
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  #11  
Old 02-03-2008, 11:11 AM
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don't claim to have any 300WM experience, but i've heard a lot of people say Reloader 22 is the ticket for the 300WM. i would try a powder that is a tad slower than what might be optimum to get better load density. this usually helps with consistent velocities. i recommend H1000 for your application. on Hodgdon's site, it not only gives the best velocity, but does it with the least pressure.
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  #12  
Old 02-03-2008, 03:42 PM
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KQguy

Standard Deviation spreads are effected by poor or inconsistant
combustion.

Some causes of this are low powder densities( 70% to 80%) wrong
primer choice,wrong powder choice, inconsistant powder charge and
poorly prepped brass.

And good groups with poor SD,s spell disaster at long range.

A good way to show this is run the balistics at the lowest velocity
with that load and then run the same test using the highest.

Just for kicks I ran the 7/08 at 3000ft/sec and added 60 ft/sec
to see what the spread was. and it came out to 14.2" @ 1000 yrds
under perfect conditions (enough for a bad hit or a complete miss at
long distance).

In cases with around 100gr or less capacity I have found times that
going to a standard rifle primer improved SDs but they also lost some
velocity (25 to 50 ft/sec).

Good luck on improving SD,s
J E CUSTOM
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  #13  
Old 02-03-2008, 09:47 PM
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In answer to your question, Sd has nothing to do with rings and bases however you indicated in your original post you were not happy with the groups you were getting at 100 yds. Tight SD does not equal tight groups at 100 yds. Long range tight SD is a must. What good quality scopes, rings,bases,proper bedding, good barrel etc has is the power to make you smile or frown when you go down to look at your target. Why did I ignore your question about lowering your SD? Because you asked it in the context that you wanted to improve your groups, I suspect if you find a load with an SD of 0.00 you will still have the accuracy problem. Sorry if I offended you.
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  #14  
Old 02-03-2008, 09:55 PM
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In answer to your question, Sd has nothing to do with rings and bases however you indicated in your original post you were not happy with the groups you were getting at 100 yds. Tight SD does not equal tight groups at 100 yds. Long range tight SD is a must. What good quality scopes, rings,bases,proper bedding, good barrel etc has is the power to make you smile or frown when you go down to look at your target. Why did I ignore your question about lowering your SD? Because you asked it in the context that you wanted to improve your groups, I suspect if you find a load with an SD of 0.00 you will still have the accuracy problem. Sorry if I offended you.
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