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Concentricity:How much ?

 
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  #1  
Old 02-08-2010, 11:30 PM
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Join Date: Jul 2004
Location: Texas
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Concentricity:How much ?

We all strive for the best quality reloads and this is just another area to deal with.

My question is- What is an acceptable amount of run out for long range accuracy?

I would like to end up with no measurable run out but I know/think this is not possible
and was just wondering what was possible and where the break point was for accuracy.

I have tested different amounts of run out with the same load and found that it did
make a difference in both accuracy and SDs. I will post the results but I was wanting
hear from the membership first.

I have improved my reloading process from an average run out of .0035 to .0005 and
cannot seem to get any better results and didn't know if this was about as good as
I can expect.

Any comments and /or suggestions would be appreciated.

Thanks
J E CUSTOM
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Old 02-09-2010, 01:56 AM
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Re: Concentricity:How much ?

for best results i sort the bulets by 1thousant runout.
best - 0-1th
acceptable 2-3
4-5 runout - not recom. for reliable shots past 800yrd.
if you paid attention to details when reloading, you can get very good at runout less then 2 thousant.
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  #3  
Old 02-09-2010, 04:52 AM
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Re: Concentricity:How much ?

J E,

+1 to 300rum said.

With my setup, it helps when sitting the bullets, I bring them down about half way and bring the ram up turn the cartridge 180 and then I sit the bullet all the way down. I kept playing and checking one by one until I was convinced that it helps.
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Old 02-09-2010, 06:21 AM
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Re: Concentricity:How much ?

For me, this is the most frustrating part of BR reloading. I use a Holland guage, and have trouble getting consistent run outs on loaded round ogives below .003.

JE - how did you get down to .0005? Are they consistent?

300rum - How are you doing run outs on bullets alone? I assume you do this prior to seating??

I believe that run outs below .003 are OK, but cannot prove it. Tough to make all of them cookie cutters.
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Old 02-09-2010, 10:32 AM
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Re: Concentricity:How much ?

Hey guys,

I have a slight problem with threads like this, in that I'm not sure we're all speaking the same language. Everyone seems to have their own methods of measuring run-out, and they're not all the same. Saw this sort of thing constantly in the QC range, with customer complaints of concentricity issues. The vast majority would turn out to be customer errors in how they were measuring what they thought was run-out.

I'd like to see some sort of standardization on how we measure, so that all our results would corelate to one another in a more meaningful manner. Don't ask me how we do that, but that's what I'd like to see.

Beyond that, I think we can all agree, less is better. But how much?

Kevin Thomas
Lapua USA
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Old 02-09-2010, 10:55 AM
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Re: Concentricity:How much ?

There are two standards going(one too many) currently.
Total Indicated Runout, and Concentricity.

TIR amounts to any and all combined as deviation from straight or true.
Concentricity amounts to ~1/2 the same -w/resp to a centerline.

Concentric ammo might not be staright, but straight ammo is concentric as well.
So IMO, low TIR should be a reloader's goal.
The best tool for TIR that I'm aware of is a V-Block/Roller similar to Sinclair's.
And I assure you, your ammo is not straight until measuring low TIR.

There are far too many abstracts affecting accuracy to set any rule of thumb. Your chamber clearances -vs- mine, your bullets, throat, headspace, cartridge diameter and length, seating depths, rifling, leade angle, primers, powder.
I say take it to diminished returns for your system,, and no further.
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  #7  
Old 02-09-2010, 10:59 AM
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Re: Concentricity:How much ?

Great Point Kevin.

I measure at the "O" give of the bullet. And I measure total runout. I don't divide it 1/2 for each direction from center. So total upand down. With Lapua brass that was annealed evenly and using full competition redding bushing dies with no expander. I can get .0005" (1/2 thou.) or less. I usually do 100 at a time and will only have 3 or 4 not make it into this group. They will be .002" or less and are used for practise.

Jeff
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