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How do I get my extreme deviation or spread DOWN?

 
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  #29  
Old 08-27-2013, 10:41 AM
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Re: How do I get my extreme deviation or spread DOWN?

I went back and looked at about a half dozen loads intended for long range use over the last few years where I was looking to get ES down. In almost all cases I got there with a change in one, or a combination of powder type, charge weight, or primer selection. I recently worked on a 300WM that produced sub .5MOA accuracy and velocity of 2750FPS using H1000 but I couldn't get my ES below 25FPS. A change to Retumbo got me 2880FPS, ES 10FPS, and equivalent accuracy. No change with any other components. I had a similar reduction in ES with my 260 Rem just by changing from a CCI BR2 to a Fed210M primer. Unfortunately there doesn't appear to be an easy formula.
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  #30  
Old 08-27-2013, 02:00 PM
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Re: How do I get my extreme deviation or spread DOWN?

Many times I have dreaded the inconsistencies of firearm to firearm even though the barrel is stamped with the same cartridge. Case in point, a friend asked for some assistance with a large 30 magnum. He stated the rifle shot 2 groups at 100. He wanted a capable 600 yard hunting rifle and one load. He brought over approximately 200 reloaded and fired brass mixed. I noticed about half the fired brass had split necks. He stated he only gets about one to two rounds with the reloaded brass before they split and thought this was normal for a large magnum. He also provided me with his dies to be used.

I started by pulling all the bullets from his reloads and factory rounds. There was a great amount of difference in pressure required to pull the bullets on the reloads. I had to hit the press arm on several to dislodge the bullet.

Normal reloading procedures used on SAAMI chambers. De-prime with a primer remover die, anneal, tumble, full length resize using provided die after removing expander ball, trim to uniform length, chamfer, expand neck using .307 expander mandrel, prime, charge, seat bullet, check runout. While seating the bullets there was similar pressure with each round. Additional check for sufficient neck tension was to push the tip of the bullet against a piece of wood with enough force to leave a noticeable indentation in the wood. If the bullet does not move there is sufficient neck tension to withstand recoil for the rounds loaded in the magazine during firing.

230 Bergers were load developed. During a cold day the owner shot the rifle at 300 yards off a bipod. One round was shot at a time and the barrel rested to completely cool between rounds for a five round group. The owner ended with a five shot group just under 2 with varying weather conditions over the period of time to make the five shots and letting the barrel cool. During load development ES was also established at 12 fps. He has not experienced a split neck since and stated this is the best shooting gun he has ever owned.

I am confident annealing provided the consistent neck tension and hardness needed for consistent results and low ES. In my 300 RUM SAAMI chamber loaded rounds are .332 with a neck chamber of .344. The difference of .012 is quite an amount of work hardening with the brass during reloading. Annealing does seem to help prolong brass life and provide more consistent neck tension and better accuracy results vs. not annealing. Will I anneal my brass after every firing in this case? Yes. Will a chamber with .004 or less clearance require the brass to be annealed frequently? Probably not if not at all. What about .008 and the frequency to anneal? One situation may require annealing while another will probably be best suited to not anneal. Sometimes apples are not apples even though the packaging or in this case barrel stamp say the same thing.
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  #31  
Old 08-27-2013, 05:41 PM
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Re: How do I get my extreme deviation or spread DOWN?

I agree with your view MMERSS.
If you HAVE TO anneal, well that is what it is, and the choices were made that led to it.
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  #32  
Old 08-27-2013, 10:51 PM
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Re: How do I get my extreme deviation or spread DOWN?

Quote:
Originally Posted by Mikecr View Post
I agree with your view MMERSS.
If you HAVE TO anneal, well that is what it is, and the choices were made that led to it.
Can't agree more. Sometimes the option to choose otherwise is not a viable option and you must play with what you currently have.
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