Home Forums Hunting & Shooting Ask The Gunwriters MD et al, need help with concentricity

i am having a degredation in concentricity after sizing in a redding bushing die (sizing button is removed). any ideas would be appreciated.
thanks in advance for your assistance.

Could be the press ram, shell holder or threads in press not concentric with the ram. Are you lubing the necks? How much are you taking the neck down?Rick.

Is the problem in the case body or neck? Its pretty hard to get it wrong on the neck with that floating TIN'd bushing

One common problem in Redding "S" dies is the bushing NOT floating. If you tighten down the nut that holds it in the die the bushing can be off-center or skewed. The bushing should have just enough room to move around slightly. That way it centers itself on the case neck.

MD

Rick,
the expander button is removed, cases lubed with imperial sizing wax. runout at the neck of oncefired cases seems to increase as much as 5 or 6 thousandths when run thru the die. i'm using a redding press.
i will try a different shellholder

Runout will also increase significantly if the degree of sizing down from a fired case is over .005"-.006". The further you have to reduce the neck, the more likelihood of runout. Redding will suggest to you that you do it in stages in some instances. Measure your fired case. If the difference between the case and your bushing is in this area, or more, use an intermediate sized bushing and bring the neck down in stages. Bushing dies are not a panacea. They do have their limitations, particularly for the sloppier factory chambers.

A wise old salt once told me that if you use no expander, you cannot expect good accuracy unless your necks are perfectly concentric......and I mean perfect. To me that means turned necks as if you have no expander plug to iron out the inside imperfections that are outside imperfections moved there on sizing, how can the bullet be seated concentricitly?
I think what you need is the redding floating tungsten-carbide expander plug.

How much are you sizing the necks? Do you load other

calibers on the same press using the same shell holder? How are you measuring the run out?Rick.
Fva, it is not necessary to have an expander ball and turn necks to have good concentricity if neck thickness is uniform. Moving imperfections from the inside of a neck to the outside would allow a concentricity gauge to measure all the imperfections.

A frequent problem with the Redding dies is the bushing DOES float. If the brass is thicker on one side or harder on one side, the neck will end up eccentric to the body. A friend told me he improved the performance of his redding die considerably by putting shim stock around the bushing to eliminate the float. The removable bushing is a great system which allows you to custom tailor your die's dimensions to fit your brass and/ or rifle chamber. A non floating bushing is preferable to one that floats however. GD

Yeah, I'm probally off base here. However having a expander button move imperfections to the outside would probally be preferable and give more consistant neck tension than using the bullet to do so. Probally give less runout if measured at the bullets tip as well.What is the purpose of removing an expander button?

Fva, measure bullet run out on the body of the bullet, not the tip. Tips can be off just from being in the box with other bullets. Just as seating depth shouldn't be measured at the tip but near the ogive.
The expander button causes many problems with concentricity. It has to be concentric along with the stem to which it is attached. That is what leads to it's problems. If the stem or expander is off the necks will also be pulled to the side. If the expander ball happens to be large compared to the amount of sizing done by the die, it can move the shoulder forward enough to cause hard chambering. The expander can iron out dents in the neck but the bullet can do the same thing which will work fine, hunting accuracy will not suffer. The worse thing to be found in the neck is a donut that should be removed by reaming in a ream die. They can be removed by turning the neck but a neck reamer and ream die is more consistant.
Greydog, the floating bushing can self align with the case. Putting shim stock around the bushing would defeat the purpose. If the case necks are concentric going into a floating bushing, they should remain the same way. May not be able to do so if the bushing is held tight to the die. One reason the Forster Co-Ax press works so well is it allows the dies to float.Rick.

MD, Rick,
i have backed the stem off 1/4 turn or so to be sure the sizing bushing is free.
the runout at the neck of the once-fired cases is .001 to .002 before sizing and .003 to .006 after ( i am using the sinclair setup).
this seems to be similar whether i use the redding mag or forster co-ax presses.i would have believed it might be better in the redding since the die does not "float", but that doesn't seem to be so.
thanks for yor suggestions

I would suggest contacting Redding and talking with them. You may have to send the die and some fired unsized and sized cases for their evaluation.Rick.

A quarter turn is a bit much. Back it off about half of that.

What is the difference in measurement between fired necks and those with seated bullets? What is the size bushing you are using?

I've got a die like that in 300WSM and I'm convinced it's the die, I just haven't gotten around to sending it back for them to look at it. Dies do get out of round sometimes during the heat treating process.

My guess is that you're using too small a bushing. Talk to the Redding boys and they will help you out.

MD

I've been trying to ignore this thread, but just have to jump in. <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

In my opinion, concentricity gauges, and such, are used to diagnose a problem. If the rifle is shooting poorly, ammunition that is "crooked" could be a cause of the inaccuracy.

That being said, I've seen some awfully crooked ammunition shoot superbly. For instance, my beloved old .280 Ackley is wonderfully accurate, but after I got a concentricity tool, I found out that my ammo was out of concntric by .004" to .008". Hell, it shot great, so I didn't source out the "problem." (What problem?)

In reading this thread, I haven't read the original poster's complaint about accuracy. This leads me to two conclusions: either he DOES have accuracy problems and is trying to diagnose the cause...or he hasn't shot the ammunition and is bothered by the lack concentricity.

MD is correct, it could be a bushing that is too small. It could also be the chamber. It can also be user error on the concentricity tool.

Basically, it all gets down to how the rifle shoots with the ammo. It the accuracy is satisfactory, forget concentricity. If the accuracy is spotty, start looking at equipment settings and the concentricity of the fired cases, sized cases and loaded ammo. The problem can appear at any of several steps.

For my varmint ammo, I use Redding Type-S neck-sizing dies, tungsten-carbide floating expander plugs and a TiN bushing that cases the slightest "kiss" of the case neck and expander plug and the case leaves the die. Works for me.

Steve

Steve is of course exactly right. Bullets can be seated pretty crooked and still shoot.

In general bullets with long shanks, shot in rifles with tight throats, will straighten themselves out before they hit the rifling. At least that is my theory about the whole deal. This doesn't necessarily mean heavy bullets for the caliber, either.

I have, however, found that short-shanked bullets (which includes most varmint-weights) shoot a whole lot better if run-out is below .004. With big game rifles I have found other factors are evidently at work, and look for .006 or less. Probably longer bullets are the key.

But set up right, Redding S dies usually produce ammo with no more than .004 bullet runout--unless, of course, the neck thickness of the brass is decidely lopsided.

At any rate, I try to keep them reasonably straight, because it's just one less factor to consider if the rifle isn't shooting consistently.

MD

Thank you for your insight.
I am ideed hoping to improve my accuracy.

I have been fighting the same problem as I think you are describing. Are you simply resizing brass to be fired in the same chamber or are you necking down brass to a new caliber? I had some 30-06 brass that was getting quite crooked by using the Redding bushing die. I determined that I was sizing too much at once. The Redding bushing aren't very good for changing calibers as they don't have much taper on entry and don't size but a portion of the neck. For best results, .004 per pass is best. If you have a giant neck in your chamber, you may have to neck size in two steps.

I don't have an opinon on whether to float or not, as either way made the ammo the same.

Dogzapper is correct in that crooked ammo can shoot just fine, however if you are making crooked ammo then something in either your technique, components or tooling is amiss. I like to eliminate those problems as it makes it easier to diagnose problems with the gun.

I have found it take lots of care to neck down or up and have straight cases. I use sizing die wax for most things, but there are better lubes for working brass this much. I use STP and it works far better. Bruno's uses Hornady Unique case lube and finds it far superior to the sizing wax. I use rapid tap for lubing the inside of case necks- especially when neck turning. It's the best product I have found for lubing brass when doing cutting work on it. I have turned a lot of brass on a lathe and it can be a real pain sometimes.