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Major runout problem.

 
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  #1  
Old 05-02-2010, 05:13 AM
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Major runout problem.

I have just loaded up 10 rounds for my new 7mm STW and I seam to have a serious run out problem. Two rounds had less than .002 runout but the rest were between .003 and .009.

I started with new whinchester brass which was neck sized with a Redding competition bushing style die with the neck expander in place to remove the dents in some of the necks. I never checked the runout on the first firing as I was just breaking in the barrel and working up a load. After this first firing I removed the neck expander and neck sized only and was a bit disappointed to find such large amounts of runout on the bullet. Runout on the case necks is better but still up to .005.

Could this be caused by inconsistent neck wall thickness? Any other ideas or solutions would be most welcome.
Thanks
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  #2  
Old 05-02-2010, 10:00 AM
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Location: medford wi usa
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Re: Major runout problem.

Others will reply that have more experience than me but I've seen posts with disapointment over that die. What I've seen is that if the die has to size down the mouth alot in one step it can get the reloader some significant runnout. It could also be caused by "some" thickness situations but I can't think that much.
I'm sure you'll get more responses (and better) but that is what I've read.
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  #3  
Old 05-02-2010, 10:20 AM
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Re: Major runout problem.

Many people will use super fine steel wool to polish the expander ball.

Also, if your die makes a squeaky sound while pulling the brass out of the die than you are not lubing the case neck inside properly. This may cause uneven friction at the neck and could throw your case out of wack.
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  #4  
Old 05-02-2010, 03:12 PM
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Re: Major runout problem.

Several things cause bullet run-out, doubtful that a shiney expander can fix any of them.

When some rounds have little runout but others do it's commonly due to poor case necks and no die change can fix that. To "fix" such necks, many of us lightly turn our necks, skimming off maybe 60-80% of the neck circumference just to even things up a bit.

Another common cause of run-out is having too much "bullet tension." Or more accurately, too much difference between the bullet and neck diameter. Any difference greater than about 1 1/2 - 2 thou means absolutely nothing to actual bullet tension but it does greatly increase the required seating pressure. Increased seating pressure almost always increases runout.

The shape of an expander button can increase the rate of bent necks. A long bearing surface, such as what we have in Lee's expanders is best while a "ball" is worse. A ball has minimul neck contact which allows even slight variations in neck thickness and/or hardness to give way a bit more in that spot and that drifts or "bends" necks in that direction, at least somewhat.

Non-concentric sizer and seater dies can do it but since you are getting some good rounds mixed in with the poor ones make that seem unlikely for you.

Bottom line, it's much more likely your's is coming from the cases themselves.
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Old 05-02-2010, 05:05 PM
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Re: Major runout problem.

Thanks a lot for that.

I donít believe that itís the expander button thats causing the problem as after the last firing I removed the button and ran the neck into a bushing that should give me .002 neck tension.

Excuse my ignorance but if I do try turning the necks would I need to turn the inside or outside or both?

Also, I have not trimmed any of these cases for length as they are still shorter than my chamber. If the necks are out of square could that cause the problem?
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Old 05-02-2010, 06:51 PM
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Re: Major runout problem.

Quote:
Originally Posted by whin4 View Post
Thanks a lot for that.

I donít believe that itís the expander button thats causing the problem as after the last firing I removed the button and ran the neck into a bushing that should give me .002 neck tension.

Excuse my ignorance but if I do try turning the necks would I need to turn the inside or outside or both?

Also, I have not trimmed any of these cases for length as they are still shorter than my chamber. If the necks are out of square could that cause the problem?
You will need an outside turner. An inside turner will do no good. Hornady makes a hand outside turner that works very well. An out of square case mouth can also cause problems and should be corrected. Good luck......Rich
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  #7  
Old 05-02-2010, 06:55 PM
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Re: Major runout problem.

Quote:
Originally Posted by whin4 View Post
Thanks a lot for that.

I donít believe that itís the expander button thats causing the problem as after the last firing I removed the button and ran the neck into a bushing that should give me .002 neck tension.

Excuse my ignorance but if I do try turning the necks would I need to turn the inside or outside or both?

Also, I have not trimmed any of these cases for length as they are still shorter than my chamber. If the necks are out of square could that cause the problem?
You will need an outside turner. An inside turner will do no good. Hornady makes a hand outside turner that works very well. An out of square case mouth can also cause problems and should be corrected. Good luck......Rich
p.s. Try seating the bullets by small increments while rotating the case maybe 6-8 times. This will compensate somewhat for any alignment problems with your dies.
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