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Concentricity..Issues or me?

 
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  #8  
Old 04-06-2005, 06:26 PM
 
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Re: Concentricity..Issues or me?

I think your right. Got the right bushing in the mail my way so I can try that. Tight now I only have bushings if I neck turn. I will say...The few cases I neck turned and resized..Then seated..The problem was .002 or less.

Thanks

Joe
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  #9  
Old 02-04-2011, 12:28 AM
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Re: Concentricity..Issues or me?

Quote:
Originally Posted by ;67709
Ok..I've spent what I believe is the utmost care in prepping my (new) Lapua case 6.5-284 Cases. I ran the necks over and Sinclair Concentricity gauge and had .001-.002 runout on the necks if that! Now..Seating a few bullets in those cases I'm getting .003 on some and up to .006 on the others. I'm using a Redding Comp seater die and the proper shell holder.

Why am I getting this runout up to .006 on some cases and not others. The bullets are Sierra 142 gr HPBT match kings. None of the necks are turned and all were sized with a Redding Standard F/L die with expander ball.YUK I figured this was OK because of the low runout on the necks after sizing.

Any advise would be great. Let me know if I left out any important info


Oh..Neck thickness on all cases was right on the money with .001 or less vari.
Lab
You are compacting the same brass that gave a proper neck size for a 7mm, to 6.5mm. That brass doesn't go away.

You will probably either have to get a neck reem at 6.5mm or turn them after resizing in order to get a consistent neck diameter after loading.

Depending on your chamber this excess brass may very well create a dangerous over pressure situation so be very leery of firing those that are showing the .003 over size.
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  #10  
Old 02-04-2011, 05:59 AM
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Re: Concentricity..Issues or me?

Neck consistency is a bugaboo for many of us. I can accept .003" or less. If more than that, I cull out the excesses and use them for sighters.

First of all, brass must be fired once or twice to fit the chamber. Good bushing type sizer and micrometer seater dies are a must. The seater die ogive cup must be deep enough so that the meplats do not touch. I put a touch of Prussian blue on a bullet tip to find out whether there is contact. Necks must be first turned. Even sizer bushings can be faulty. Try this: Size the case once, then turn it 180 degrees in the shell holder and size it again. Do same with the seater; lower the bullet about 70%, turn in the shell holder and lower it to desired OAL. Theory is that increases consistency all around. I have no way to prove this theory.
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  #11  
Old 02-04-2011, 08:16 AM
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Re: Concentricity..Issues or me?

Quote:
Originally Posted by Gene View Post
.

Try this: Size the case once, then turn it 180 degrees in the shell holder and size it again. Do same with the seater; lower the bullet about 70%, turn in the shell holder and lower it to desired OAL. Theory is that increases consistency all around. I have no way to prove this theory.

+1 on this. I go a little further though. When sizing I will lift the ram just enough to free the case and rotate the case about 1/4 turn 4 or 5 times bringing the ram back down each time. I do the same for seating a bullet.

I have proved this works many times by measuring runout on rounds I loaded with this method and rounds loaded with one sizing and seating stroke. Using this method I get my rounds ALL within .003 with the vast majority .001 or less. If I occasionally get a .004 I can usually put it back in the seater and bring the ram down 8 or 10 times rotating it just a little each time and bring it to .003 or less. This is with a long 338 Khan, shorter cases should work even better.

One other thing is I do not use an expander ball. They tend to put stress on the neck / shoulder when pulled out.
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  #12  
Old 02-04-2011, 08:40 AM
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Re: Concentricity..Issues or me?

As a matter of routine I size "New" brass with the turning sizer from Sinclair and then turn all necks
the same before ant load sizing is done.

This seems to start the brass out concentric before any loading or firing can permanently
shape them out of concentric.

If I start sizing before turning the neck thickness difference seams to move it to the thinner side
throwing it off center more.

It seems even more important to do this if I am sizing down a case from a larger parent case.

It will not eliminate the problem but it does help to minimize it.

J E CUSTOM
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  #13  
Old 02-04-2011, 03:50 PM
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Re: Concentricity..Issues or me?

Quote:
Originally Posted by ;67709
I ran the necks over and Sinclair Concentricity gauge
Which 'concentricity' gauge are you using?

Quote:
Originally Posted by ;67709
None of the necks are turned and all were sized with a Redding Standard F/L die with expander ball
Not the easiest path to low runout.

Quote:
Originally Posted by ;67709
Neck thickness on all cases was right on the money with .001 or less vari
How did you measure this?

It 'seems' most like a seating issue, but I wonder about the above first.
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  #14  
Old 02-04-2011, 04:07 PM
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Re: Concentricity..Issues or me?

The origanal post was in 05.
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