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Excessive bullet run out. How to remedy?

 
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  #50  
Old 07-12-2012, 09:57 AM
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Location: Santa Rosa, CA
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Re: Excessive bullet run out. How to remedy?

This article from the Blog section of 6mmBR, November 2005 is not directly related to concentricity gauges, but I thought it was worth a read:


"RELOADING TIP--Neck Tension vs. Time: We've learned that time (between neck-sizing operation and bullet seating) can have dramatic effects on neck tension. Controlling neck tension on your cases is a very, very important element of precision reloading. When neck tension is very uniform across all your brass, you'll see dramatic improvements in ES and SD, and your groups will shrink. Typically you'll also see fewer fliers.

Right now, most reloaders attempt to control neck tension by using different sized neck bushings. This does, indeed, affect how hard the neck grips your bullets. However, James Phillips recently discovered that another critical factor is at work. He loaded two sets of 22 Dasher brass. Each had been sized with the SAME bushing, however the first group was sized two weeks before loading, whereas the second group was neck-sized just the day before. James noticed immediately that the bullet seating effort was not the same for both sets of cases--not even close.

Using a K&M Arbor press equipped with the optional Bullet-Seating Force Gauge, James determined that over twice as much force was required to seat the bullets which had been neck-sized two weeks before. The dial read-out of seating force for the "older" cases was in the 60s, while the seating force for the recently-neck-sized cases was in the 20s. (These numbers correspond to pounds of force applied to the bullet). Conclusion? In the two weeks that had elapsed since neck-sizing, the necks continued to spring back (get tighter) and stiffen. Lesson learned: for match rounds, size ALL your cases at the same time. If you want to reduce neck tension, load immediately after sizing."
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  #51  
Old 07-12-2012, 10:03 AM
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Join Date: Dec 2005
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Re: Excessive bullet run out. How to remedy?

Quote:
Originally Posted by Goofycat View Post
IMHO, the worst possible use of a concentricity gage is for bending the ammo straight. It can be done but the pressure can also damage thin jacketed bullets in the effort. The best use of a gage is to find where (and why) your runout is coming from so you can correct the cause. First check your sized cases; NO seater can make straight ammo in bent-neck cases.
Good information.

All the crooked ammo I straightened up was done with a bullet puller. A .338" bullet collet was used to hold handloaded .30-.338 Win. Mag., 7.62 NATO and commercial .308 Win. ammo by the neck. Their neck diameters were somewhere between .336" and .338" so the case neck holding the bullet was well supported all the way around. Accuracy went from 2 MOA to 1 MOA at 600 yards with the NATO and commercial .308 stuff. Straightened .30-.338 Win. Mag. ammo with new cases went from just under 2 MOA at 1000 to 3/4 MOA after bending the case necks straight in the same collet. If the bullets were damaged in any way, I don't think it was enough to make a difference. Straight ammo (.003" bullet runout or less) shot as accurate as the ammo with straightened bullets.
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  #52  
Old 07-12-2012, 10:10 AM
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Join Date: Apr 2010
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Re: Excessive bullet run out. How to remedy?

Quote:
Originally Posted by Goofycat View Post
This article from the Blog section of 6mmBR, November 2005 is not directly related to concentricity gauges, but I thought it was worth a read:


"RELOADING TIP--Neck Tension vs. Time: We've learned that time (between neck-sizing operation and bullet seating) can have dramatic effects on neck tension. Controlling neck tension on your cases is a very, very important element of precision reloading. When neck tension is very uniform across all your brass, you'll see dramatic improvements in ES and SD, and your groups will shrink. Typically you'll also see fewer fliers.

Right now, most reloaders attempt to control neck tension by using different sized neck bushings. This does, indeed, affect how hard the neck grips your bullets. However, James Phillips recently discovered that another critical factor is at work. He loaded two sets of 22 Dasher brass. Each had been sized with the SAME bushing, however the first group was sized two weeks before loading, whereas the second group was neck-sized just the day before. James noticed immediately that the bullet seating effort was not the same for both sets of cases--not even close.

Using a K&M Arbor press equipped with the optional Bullet-Seating Force Gauge, James determined that over twice as much force was required to seat the bullets which had been neck-sized two weeks before. The dial read-out of seating force for the "older" cases was in the 60s, while the seating force for the recently-neck-sized cases was in the 20s. (These numbers correspond to pounds of force applied to the bullet). Conclusion? In the two weeks that had elapsed since neck-sizing, the necks continued to spring back (get tighter) and stiffen. Lesson learned: for match rounds, size ALL your cases at the same time. If you want to reduce neck tension, load immediately after sizing."
Now, how do you feel about neck tension after bending, flexing, stretching your case neck using the bullet as a lever?

It's a trade-off and you need to decide for yourself which works best for you.

In the grand scheme of LR Hunting, most of us need more range time and less straightening.

-- richard
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  #53  
Old 07-12-2012, 03:02 PM
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Re: Excessive bullet run out. How to remedy?

Quote:
Originally Posted by rscott5028 View Post
Now, how do you feel about neck tension after bending, flexing, stretching your case neck using the bullet as a lever?
Good question....

I feel folks might consider sizing their fired cases such that the neck and body stay in alignment as much as possible as the fired case dimensions are changed. And change those dimensions as little as possible
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  #54  
Old 07-12-2012, 08:04 PM
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Join Date: Dec 2005
Posts: 2,114
Re: Excessive bullet run out. How to remedy?

Pressing on a bullet whose case isn't supported anywhere in front of the shoulder-body junction is not a good idea. Especially with lighter neck tension on it.
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