Concentricity Problems

[dan46n2]

I just received my Sinclair concentricity tool today and started checking the .223 rounds I loaded. I used a Giraud to trim the brass. I am getting about 20% less than .004, 15% less than .005, and 65% more than .005. I had a lot of problems with uneven chamfer using the Giraud because I was inserting the cases too slowly. Would an uneven inside chamfer account for this much variation in concentricity? Brass is once fired LC.

Also what should I do with the rounds above .005, save the bullet, powder, and primer and toss the brass or pull the bullet and try to reseat it?

 

[Suasponte]

Re: Concentricity Problems

What are you loading for?

Terry

 

[MitchAlsup]

Re: Concentricity Problems

Why not check the necks for concentricity as they come out of the sizing die? I would not blame the chamfer step if the necks are already nonconcentric.

 

[Hummer]

Re: Concentricity Problems

check fired cases right out of rifle.
then size them and run them again.
then turn necks and run them again.

dies are notorious for messingup neck alignment.

 

[dan46n2]

Re: Concentricity Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">Why not check the necks for concentricity as they come out of the sizing die? I would not blame the chamfer step if the necks are already nonconcentric. </div></div>

So it's normal for 65% of LC brass to be over .005 inches up to .010 in concentricity variation?

 

[dan46n2]

Re: Concentricity Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hummer</div><div class="ubbcode-body">check fired cases right out of rifle.
then size them and run them again.
then turn necks and run them again.

dies are notorious for messingup neck alignment. </div></div>

I was thinking about getting the Pumpkin, do I need an expander die for it? I've never used a neck turner.

 

[Brain]

Re: Concentricity Problems

You need to figure out at which stage of loading the runout is being introduced.

1. Check fired case
2. Check sized case
3. Check loaded round just aft of the ogive

 

[dan46n2]

Re: Concentricity Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: suasponte</div><div class="ubbcode-body">What are you loading for?

Terry </div></div>

This is for my ARs (Colt, BCM, etc, not match rifles), just looking for 1 moa or better accuracy.

At this point all the brass has been sized so I can't check the just fired cases right now.

 

[Victor N TN]

Re: Concentricity Problems

Have you been cleaning the insides of your case necks? I use a new bore brush in a RCBS screwdriver handle and twist while pushing it in. Then twist while pulling it out.

If you feel you must turn case necks, I'll try to help you through it. But for a non-match rifle, I don't think I would go that far. But that's up to you.

Have you tried shooting any GOOD facrory or match ammo through it?

 

[Greg Langelius *]

Re: Concentricity Problems

I shoot rifles with SAAMI chambers exclusively.

I did some testing regarding concentricity in my rifles and found that the dismal story my borrowed concentricity gauge was telling me had little to no relationship to the accuracy of the ammunition. This was precisely why I had decided to stick with SAAMI chambers, and the experiments convinced me my life was going to simpler for it.

Concentricity is crucial to accuracy in other instances; ones where tight chamber/tight tolerance rifles are being shot with meticulously made ammunition, with intent to achieve small group sizes.

For factory rifles with factory chambers, the rifle itself limits accuracy to the point where this limit overshadows many of the more meticulous steps in handloading.

A new piece of measuring equipment can be very informative, but sometimes the information can create the impression that a problem exists when in fact that very real problem has little or no significant bearing on our activities.

Where measurements are involved, I regain my sense of priorities by examining the most important measuring tool, the target.

If you can correlate a relationship between what the concentricity gauge is telling you, and what the target is telling you; then the problem is significant. Otherwise, the concentricity information is not significant.

Meanwhile, I wouldn't toss brass with concentricity issues, I'd be saving it for fouler/sighter rounds. Brass is not cheap.

Greg

 

[MitchAlsup]

Re: Concentricity Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dan46n2</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">Why not check the necks for concentricity as they come out of the sizing die? I would not blame the chamfer step if the necks are already nonconcentric. </div></div>

So it's normal for 65% of LC brass to be over .005 inches up to .010 in concentricity variation? </div></div>

My point (and Hummer's point) was that you have to isolate where the nonconcentricity is comming from. Then you should also add Greg's comments about correlating nonconcentric rounds with good or bad groups. Until you do these steps you don't know how much it is costing you in group size, or where it is showing up in the reload cycle.

 

[dan46n2]

Re: Concentricity Problems

Good news at last, I'll shoot them and see how accuracy is affected if at all.

 

[dan46n2]

Re: Concentricity Problems

I've been doing some more reading on the subject and it seems that unless you have a custom match or very tight chamber, concentricity has almost no effect on accuracy. Knowing how to correct it is good though, I'll have to do that for my .308.

 

[sobrbiker883]

Re: Concentricity Problems

What kind of accuracy are you getting with the stuff you've been loading so far?

Personally, I roll a round on a mirror and if it visibly wobbles it goes in a fouler/sighter pile.

Unlike many, I do not enjoy reloading, I reload because I enjoy shooting, so I've cut down on the processes that in my case really don't make much difference. If I knew I could shoot the difference between .004 and .006 runout, I would worry about it, but I know I couldn't.

It seems from reading some of your posts that you are trying to get benchrest rounds from a Dillon, and all I can say is if that were practical that's how all the benchrest guys would load. Especially if you are trying to size, trim, prime, charge and seat in a production manner.

 

[dan46n2]

Re: Concentricity Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">What kind of accuracy are you getting with the stuff you've been loading so far?

Personally, I roll a round on a mirror and if it visibly wobbles it goes in a fouler/sighter pile.

Unlike many, I do not enjoy reloading, I reload because I enjoy shooting, so I've cut down on the processes that in my case really don't make much difference. If I knew I could shoot the difference between .004 and .006 runout, I would worry about it, but I know I couldn't.

It seems from reading some of your posts that you are trying to get benchrest rounds from a Dillon, and all I can say is if that were practical that's how all the benchrest guys would load. Especially if you are trying to size, trim, prime, charge and seat in a production manner.
</div></div>

I haven't shot any of the rounds loaded on the Dillon yet, just got the press about a month ago and am still working on these issues I've had. I'm not really trying to get benchrest quality rounds, but I want to get them as good as I can at a high volume in as short amount of time as I can. If I can cut down concentricity by half with a new comp seater for example that would be worth it to me. However as others have pointed out I may not even notice a differnce with standard chambers. I am still trying to improve though so I can know how to make my .308 rounds as accurate as possible for my precision rifles. Also it brings some satisfaction to know that I can make potentially accurate ammo even if my rifle can't tell the difference.

 

[Larry Burchfield]

Re: Concentricity Problems

I may have missed it but what kind of sizing die are you using?
larryj

 

[deadlyswift]

Re: Concentricity Problems

Dan,
How far are you shooting? If shooting at 100yrds runout doesn't really have that much affect at this range. Also I have seen some lapua brass have a lot of runout in some of there cases. Not too many but some. I usually set these aside for fouling or sighters. If you are getting .004 or .005 runout now there isn't much you can do to get rid of it. even by turning the necks. If your necks have .004 to .005 runout check the case back just above the web of the case. You will probably find a huge amount of runout there. As you shoot the cases this runout from the head of the case moves foward to the neck or mouth of the case. Most Of the time if runout is present from the start it will always be present. To be honest if your not shooting a tight neck chamber I wouldn't even waste the time to turn the necks. The best thing to do would be to use a inside neck reamer get the ID of the neck as round as possible.

 

[dan46n2]

Re: Concentricity Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: larryj</div><div class="ubbcode-body">I may have missed it but what kind of sizing die are you using?
larryj
</div></div>

It's a Dillon steel FL sizing die, Dillon seater also.

 

[Larry Burchfield]

Re: Concentricity Problems

If you want to get your runout better than what you have you will probably have to go to a benchrest type sizing die or one like the redding bushing die.
IMHO
larryj

 

[vinconco]

Re: Concentricity Problems

Actually, a lot of runout that you measure is caused by case wall thickness variations. When fired, the case expands more on one side than the other. New cases when loaded will generally exhibit less runout than after they are fired because of this. BR shooters in the past would mark the case head to orient the case so that the "bannana bend" would be in the same position for each round when chambered. Measuring for case wall thickness variations and sorting the brass can eliminate the some of the worst cases.

 

[110len]

Re: Concentricity Problems

If your decapping die has an expander ball get rid of it. If you are shooting a semi-auto and it's denting your case neck/mouth, try a Lee collet die. It's cheap and works great. Check your shell plate for wobble as well. Also, for the Dillon presses there is a modification you can do that will lock the toolhead in place so it doesn't wobble.
Len

 

[Augustus]

Re: Concentricity Problems

If you have a concentric chamber your brass should have less than .001 runout on fired brass. Any differences in neck wall thickness will be pushed to the inside upon firing. You can inside neck turn and fix any variations. A lot of the concentricity issues are induced during the resizing process, especially if using a die that resizes the necks excessively. When this occurs the expanding process put a lot of pressure on the neck and shoulder potentially causing runout.
Many seating dies cause run-out. I have an RCBS comp seating that induces about .003 runout. I changed to a Forester and the problem went away.
If you get a Redding type S sizing die and fit it with a bushing that allows you to do away with the expander, then get a good seater die, most of your problems should disappear. If you are still having problems I would inside neck turn the fired brass before sizing. Hope this helps.