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accuracy consistency problem

 
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  #1  
Old 07-25-2013, 05:44 PM
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Join Date: May 2013
Posts: 142
accuracy consistency problem

I'm trying to develop a load for my 300 win mag, but I'm having accuracy consistency problems. I'll get a 3/8" group one day and with the same load I'll get a 1 1/2" to 2" group the next day. One day while doing an OCW test, I got 4 out of 5 bullets in a bug hole with a rather warm barrel. The next day that load was over an inch grouping.

I'm using Norma brass and have tried Winchester and Remington brass. I'm using CCI 250 LRM primers and have some Remington 9 1/2 LRM primers, which I haven't tried yet. I do have a second box of CCI primers. Since primers aren't available, I'm stuck with CCI or Remington. I've deburred the flash hole, used a primer pocket uniformer, weighed and sorted the brass, measured and sorted the bullets by bearing surface, deburred the case mouth, cleaned the brass with a sonic cleaner, I'm using a balance beam scale and double check with a digital scale. I'm using the same lot number of powders.

I'm shooting off of a stable bench with sand bags. I've thoroughly cleaned the bore with Boretech copper remover. Its a brand new match grade Benchmark barrel. The stock has been bedded, the action trued and a Timney trigger installed with about a 2 3/4 pound pull. I think that I'm not flinching.

The best results are with Nosler 180 grain accubonds with RL22 and Barnes 168 grain TTSX with IMR 4831, they just are not consistent. I've tried SAAMI spec for overall length for both bullets and loading the Barnes 70 thou off the lands and the Noslers 20 thou off the lands. I recently bought a Magnetospeed chronograph to know what the velocities are doing. I'm getting ESs of 40 to 90 fps. Today one group was 9/16", but the ES was 30, so I know that the grouping will not be repeatable.

Anyone have any ideas on what is going on??? Or what to try???

Thanks.

Last edited by dmax1800; 07-25-2013 at 05:56 PM. Reason: added text
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  #2  
Old 07-25-2013, 05:59 PM
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Join Date: Feb 2007
Location: Townsend, Montana.
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Re: accuracy consistency problem

Quote:
Originally Posted by dmax1800 View Post
Or what to try???

Thanks.
H-1000 and a 215 Berger .-040" off the lands. Use the Norma, or WW brass and start with 73 gr and work toward 77 watching for pressure.

Clean very well first to remove all the copper from the Barnes with BoreTech, and don't oil the barrel after, just dry patch it dry.

Jeff
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Old 07-25-2013, 06:31 PM
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Join Date: May 2013
Posts: 142
Re: accuracy consistency problem

I forgot to mention that my rifle is a Winchester model 70. It has a blade ejector. If the cartridge is very much longer than SAAMI spec of 3.340 inches, the second round will hang up on the bottom of the ejector and will not chamber. I've been alright with 3.350 inches, but any longer and the second round will be a problem. I'm going to use the rifle hunting, so I probably need the second round just in case.
I'm trying to find a load that will deliver 3/4" to a max of 1" consistently. I believe the rifle is capable, its just finding a load.
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  #4  
Old 07-25-2013, 06:40 PM
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Join Date: Feb 2007
Location: Townsend, Montana.
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Re: accuracy consistency problem

All my rifles are hunting rifles. I single feed the repeaters and have for years. When prone for a long range shot it is not that hard to drop a follow up in. My newest rifle is a single feed.

I do think you will find the load to do what you want. But if you live by the limits of your mag box it may not be with the best long range bullet.

Jeff
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  #5  
Old 07-25-2013, 07:05 PM
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Join Date: Jan 2012
Location: Greencastle, PA
Posts: 254
Re: accuracy consistency problem

I recently had this same problem with a .260 rem using H4350. H4350 is supposed to be the go to powder for the .260, well my rifle will not shoot H4350 with 130 bergers. I switched powders and bam...everything is repeatable and consistent.

My rifle would do the exact same thing. I run an OCW and get a good node, load up a few with different seating depths, take the best one and load up 10-20 rounds and the next time I shoot...it is all over the place. Start over, find a different node, etc, etc. I went through a bunch of powder and bullets (not cool in this current situation) trying to figure it out.

I used 4 different primers, 3 different bushings, and never once thought about changing powders since I know two people who have the exact same rifle.

The new powder will shoot with different seating depths, primers and bushings. I can't make it shoot bad now, everything works. Crazy.
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  #6  
Old 08-10-2013, 12:09 PM
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Join Date: May 2013
Posts: 142
Re: accuracy consistency problem

I think I found the problem. In another thread I asked for recommendations for different bases and rings. I was using Weaver bases (aluminum) and Warne QD rings (steel). Trebark and Bruce_Ventura suggested I try Burris signature rings and bases. So I took their advice and got a set. This morning I tried the same load with 3 different primers and at least got fairly consistent groupings: 1" to 1 11/`16" and most of them were 1" to 1 3/8". NO FLIERS!!! I think either the combination of aluminum and steel or the Warne QD rings was causing scope stress and resulted in fliers.
I still have to work up a better load, but at least things seem to be consistent now.
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  #7  
Old 08-10-2013, 12:47 PM
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Join Date: Jul 2013
Location: Maine
Posts: 58
Re: accuracy consistency problem

I am interested in this issue. I can understand a consistency issue due to rings and bases that do not match, yet I don't see why you would get such wide ES readings. I do not currently load for the 300 wm, but I recently picked up one in the Stevens M200 platform to build over the winter. I am interested to see how this turns out for you.
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