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How to reduce bullet runout?

 
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  #1  
Old 10-26-2008, 04:37 PM
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How to reduce bullet runout?

I loaded up some 6mm berger 88gr high bc's for the 243 today and made a tool to measure bullet runout. I was amazed to find that i'm getting up to 12 thou runout near the tip.

Some of the things i noticed:
1. due to the sharp profile of the bullet, the seating plug does not touch it on the ogive, but the tip of the bullet sticks through the hole in the seating plug, causing the edge of the hole to be the only contact with the bullet, leaving a ring near the tip of the bullet. (standard lee seating die)
2. I'm getting quite a bit of runout on the case neck after bumping shoulders back with the lee full length sizing die.
3. i was trying to get into the lands, but due to the sharp profile, i cannot get into the lands and still fit into the magazine. At 74.9mm COAL i feed properly and seat 2/3 calibre into the neck without touching the lands. (i would have liked to get at least a calibre depth into the case neck, but that would take me miles off the lands.

I am not doing benchrest with this setup, but i need to get MOA accuracy or better without breaking the bank (bank's already broken:()

Would it help to straighten them out after loading?

Any advice much apreciated.
P
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  #2  
Old 10-26-2008, 05:49 PM
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Re: How to reduce bullet runout?

You can get MOA out of even basic lee dies.

Don't measure runnout near the tip....measure it about 1/2 way between the case mouth and the ogive of the bullet.
Sounds like the seater is actually working fine. When it pushes on the very tip of the bullet it gets hard to seat straight.
You need to get your die to make straighter cases during sizing. Most likely the expander ball is pulling the neck off center.
You need to get that expander ball centered better in the die. On a lee die the first thing I do is turn the lock ring upside down so the funky O-ring is out of play. Then you need to fiddle with the expander stem till it is centered. If I remember the lee die has a lock nut on top that crimps or holds the stem in place. Try loosening it slightly and bringing a piece of brass up to the expander ball to hold it centered then tighten the nut. Try sizing 5 pieces of brass and see if it improved. If not you may have to keep loosening and tightening till you get the stem centered. Eventually I think you'll find a sweetspot where it is centered. Early hornady dies locked the expander like the lees and I've loosened and tightened a number of the hornady's until I got them making really great runnout. It sounds crazy but if you get an expander centered well they can make match grade ammo and certainly ammo that can go moa. BTW--if your gun is up to it and likes your load ammo with .005" runnout and under can easily go moa.
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Old 10-26-2008, 07:52 PM
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Re: How to reduce bullet runout?

"2. I'm getting quite a bit of runout on the case neck after bumping shoulders back with the lee full length sizing die."

Low run-out with bottle neck cases depends almost entirely on straight necks and that means both good brass and excallant sizing/expanding methods. ALL conventonal expander buttons tend to pull necks out of line but Lee's long expander section is perhaps one of the best conventional types.

For factory rifles, light neck turning can help but don't bother cutting more than about 75% of the neck circumference if you do it. We can turn a perfectly concentric neck that is such a lousy fit in the chamber it may well be worse for accuracy, not better.

With carefully selected and lightly neck turned brass, I prefer to FL size with a body die which doesn't touch the neck at all. Then I usually use a Lee Collet neck sizer die because it makes the straightest necks I've been able to produce. If I'm neck sizing with the Lee die alone, and I often do, I dispense with the body die.

IF I have to use a conventional FL sizer, I first decap with a universal decapper and remove the expander/decap rod from my FL sizer. After sizing, I use a Lyman "M" expander die which works by pushing IN rather than pulling OUT and that makes necks almost as straight, on average, as the Lee Collet neck sizer.

We may measure run-out any way we choose but I disagree with Kranky's method only because it will automatically give lower readings than the bullets actual, full length tilt.

I prefer to measure bullet run-out as near the tip as possible so I can to see the maximum difference possible. That way I can more easily gage the results when I change methods or tools. When my cartridges read .002" or less TIR, I know I have some straight ammo! (Total Indicated Run-out is twice the actual tilt of the bullets.)

Can we bend the bullets to improve run-out? Sure. If the seating depth is slight it may even help accuracy. But, if the bullet is seated deep, I fear we may get a "straighter" round at the expense of some degree of compression damage to the bullet's thin jacket and soft core. I prefer to work on my cases, loading tools and methods for straighter ammo rather than bending them straight.

Good luck.

Last edited by boomtube; 10-26-2008 at 07:56 PM.
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  #4  
Old 10-27-2008, 04:17 AM
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Re: How to reduce bullet runout?

Boomtube, there is a lot of meat in your response and i will investigate your methods. I just used the suspect rounds this morning without messing with them any further. at least now i am back to fire formed cases and i can start by measuring after every step in the process to see how the runout devellops during the whole process.
I will post my findings.

Thanks
P
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  #5  
Old 10-27-2008, 09:04 AM
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Re: How to reduce bullet runout?

Don't the Lee's collet neck dies help with this problem?
Shoot it and then just resize the neck.

I'm really asking, not implying that I know.
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  #6  
Old 10-27-2008, 09:10 AM
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Re: How to reduce bullet runout?

Quote:
Originally Posted by Limbic View Post
Don't the Lee's collet neck dies help with this problem?
Yeah, it does. Perhaps it's use is the most important single tool I've used for straighter necks. But, there is a lot more that can be done to get run-out averages down to the lowest possible numbers.

A good seater helps quite a bit too. Seaters by Forster (my choice) or Redding won't make case necks any straighter but they sure won't add any run-out to good cases. Their expensive micrometer seating heads add nothing to concentricity but they do make it easy to do small seating adjustments when the right seating depth is known.

Last edited by boomtube; 10-27-2008 at 09:19 AM.
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  #7  
Old 10-27-2008, 10:47 AM
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Re: How to reduce bullet runout?

I know this is going to ruffle a few feathers but it cannot be helped. First everything starts with the sizing operation think of it as a foundation of a house. Make sure the sizing die is centered when installing it in the press then ensure that each round has the right amount of lube otherwise you will have inconsistent sizing of the brass and that is very bad juju for accuracy. All of my Wilson sizing dies are cut with the finish reamer that was used to chamber the rifle but in your case this will be impossible to do so just order the Wilson seating die and an arbor press (forget about using a conventional press).

It is much easier to find the systemic cause of your problems rather than try and correct after the fact but this device will help you do both Concentricity Gauge . In the former you can check your concentricity and the later will enable you to correct it if needed. I am a 1k BR shooter and like to win because losing sucks but that being said your accuracy problems might be helped by this and then again it may not make any difference at all. This will be however, another step in the right direction to achieve smaller groups and bring out the accuracy potential of the rifle.
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