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Reloading Berger Bullets


Case Cocentricity

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Unread 11-30-2008, 06:06 PM
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Join Date: Oct 2007
Location: Mountians of SW NC, near Asheville
Posts: 1,595
Re: Case Cocentricity

Dry, I don't think ANYTHING in reloading is a predictable fact. It's all cut and try. If it works, great, if it doesn't it may work next time! Who knows.... And I make no claim to be a expert, been at it over 40 years and still learning.

That said, no die used today will make the cases work better in another die tomorrow so, no, even if the Lee should do you better with your new brass it will have to be used next time too.

I suspect the "problem" with bushing dies is that the necks enter the bushing while the body of the case is still not touching the die walls. That means that any soft or thin spots in the neck will give way more and the neck will drift to that side. I think. Most of the time anyway.

Lee's Collet die is unique. It has a bullet sized mandrel which also serves as the decapping rod. The mandrel is pretty well centered in the die body so the necks get a good chance of being squeezed down and kept straight. IF the necks are concentric, so the inner and out diameters are also concentric.

I won't con you, nothing in this life is perfect including Lee's Collet neck die. It has a learning curve so those who are not willing to take the time and effort to learn to use it will be better served with some other type die. Other dies are pretty much a conventional "shove it in and pull it out" design while the Lee requires a developed feel to be consistant with the inside diameter. And, SADLY, some of them have internal rough places that may need to be polished smooth with a split dowel and sandpaper spun in an electric drill. Still, personally, the advantages of the collet neck dies out weight the disadvantages, by a lot, and at much less fuss and expense.

I have no personal experience with anyone's bushing dies. Just know what I read on the web about them producing bent necks, as your's does. I KNOW the only way to get consistant bullet tension, as most people figure it, demands that the necks be turned to a constant thickness. Seems ALL of the magazine "experts" love bushing dies but I sometimes wonder about some of them too....

Good luck!
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Unread 11-30-2008, 08:33 PM
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Join Date: Oct 2006
Posts: 624
Re: Case Cocentricity

The brass gets concentric when fire formed.

It can stay concentric when sized.

If it is not concentric, sizing will not make it straight. When the neck of the case goes in the neck of the die, nothing is holding the body of the case.

If you buy a concentricity gauge, you will see that the errors are:

.004" from pulling an expander ball through the single step sized neck.
.001" sizing with a bushing die with a chamber .006" larger than the loaded neck.
.001" seating a bullet into an unsupported case.

Non concentric ammo can only open groups from ~ 2" to ~ 4" larger at 100 yards with ~.004" eccentric ammo.
If the ammo gets any worse, the chamber will bend it straight.

Don't buy a concentricity gauge. They come with a little fortune cookie message that says, "You will probably find the expander ball is causing the problem."
Just remove the expander ball, and save some money.
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Unread 12-01-2008, 09:58 AM
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Join Date: Nov 2008
Posts: 5
Re: Case Cocentricity

Thanks Clark.
It seems that the expander is the root of most case prep problems perhaps even at the point of manufacture. I will be sure to avoid them as much as possible. I think I will try turning the necks on the new cases and see if that helps. Next I will fire-form what I have loaded and see what I have and then go from there. You guys are all great for responding! I will post my results as I go along.
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Unread 12-01-2008, 11:01 AM
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Join Date: Oct 2007
Location: Mountians of SW NC, near Asheville
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Re: Case Cocentricity

"I will be sure to avoid them (expander balls) as much as possible."

Welll ... with respect, my experience with and without expanders differs from Clark's. They call them things expander balls because they expand. Sizers, conventional sizers anyway, size case necks down too far and the expanders bring them back up to very near bullet diameter before we seat bullets. If we don't expand those too small necks with an expander of some kind we will have to do it with the bullet itself and that really ain't very good.

First, it's very hard to get any flat based bullet to enter a too small mouth cleanly so the bullet heel tends to get damaged in the effort. Damaged heels are really bad for accuracy.

Next, if you recognise that a standard expander ball is unsupported and pulls the necks out of line, figure out what using a loosely supported bullet as an expander is going to do to the necks as it gets pushed into an undersized hole.

Finally, case brass is sorta thick, hard and tuff. Many bullet jackets are not so thick, hard or tuff. Using a relitively soft bullet, even jacketed, to expand a hard neck just doesn't seem good, at least not to me. To much chance to deform the bullet, at least a little bit.

Get a Lee Collet neck sizer, or a Lyman "M" expander to use with your present size die, and be done with it.

Last edited by boomtube; 12-01-2008 at 11:07 AM.
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Unread 12-01-2008, 11:29 AM
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Join Date: Oct 2006
Posts: 624
Re: Case Cocentricity

The brass comes concentric when new.

The expander ball does .004" of bending if used in the same step as when the brass is sized, but much less if the brass is already sized.
The expander ball can be used later to bell the mouth of the case for cast bullets with little effect on concentricity.

That is, if the expander ball is removed, the brass sized, the expander ball replaced, the case inserted into the die only far enough for the neck to be expanded but not sized, then the ball is not pulling when expanding, but pushing.

The reason for the big difference between pushing and pulling with the expander ball is that pushing against a shell holder is more balanced than pulling. If the shell holder is open on one side, that side hangs back in pulling and the neck is bent toward that side.

In forming 6mmPPC brass from 220Russian, a mandrel is used and never an expander. I did not under stand the difference and wrote professor Bradshaw [assistant professor back in 1994]
Load development in a benchrest rifle - rec.guns | Google Groups

The answer was pushing vs pulling.

Here is Bart Bobbit telling me how he made his own concentricity gauge:
Setting up a concentricity checker. - rec.guns | Google Groups
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Unread 12-01-2008, 12:04 PM
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Join Date: Jun 2001
Location: Potomac River
Posts: 5,070
Re: Case Cocentricity

I will add a couple of points

A fired case is only as concentric as the chamber of the rifle. There are plenty of rifles with poorly cut chambers and out of alignment chambers ( I have two of them). There are also plenty of rifles with chambers that are close to Max SAMMI so the cartridge is rolling around in there laying on the bottom of the chamber.

If you want concentric ammo you need a gauge otherwise you do not know whether you do or do not have good ammo. And you do not know why.

Finally, putting good ammo in a bad chamber will help but it does not cure a bad chamber. That is why there are a lot of custom rifles used on this forum where accuracy is a requirement. You just got to have a good chamber.
The Smokin Fur Rifle Club
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Unread 12-01-2008, 12:24 PM
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Join Date: Jul 2004
Location: Texas
Posts: 6,879
Re: Case Cocentricity

I have minimized this problem by outside neck turning.

I know you said you did not want to do that but I found that preping the
cases and doing a minimum outside turn on the necks made all the difference
when fired the first time.

The dies or the expander cannot true up the thickness varriations in the necks
so I turn them before the first firing and let the chamber true the case up.

After using this process the neck runout is as true as the chamber. Also if you
outside turn before firing you can check the chamber Cocentricity before resizing
the brass.

I only turn enough to clean up the necks the same. all brass will have some
differances in neck thickness so I true it up befor I start loading.

Just the way I do it and it works for me.
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