Major runout problem.

[whin4]

I have just loaded up 10 rounds for my new 7mm STW and I seam to have a serious run out problem. Two rounds had less than .002 runout but the rest were between .003 and .009.

I started with new whinchester brass which was neck sized with a Redding competition bushing style die with the neck expander in place to remove the dents in some of the necks. I never checked the runout on the first firing as I was just breaking in the barrel and working up a load. After this first firing I removed the neck expander and neck sized only and was a bit disappointed to find such large amounts of runout on the bullet. Runout on the case necks is better but still up to .005.

Could this be caused by inconsistent neck wall thickness? Any other ideas or solutions would be most welcome.
Thanks

 

[kraky]

Others will reply that have more experience than me but I've seen posts with disapointment over that die. What I've seen is that if the die has to size down the mouth alot in one step it can get the reloader some significant runnout. It could also be caused by "some" thickness situations but I can't think that much.
I'm sure you'll get more responses (and better) but that is what I've read.

 

[britz]

Many people will use super fine steel wool to polish the expander ball.

Also, if your die makes a squeaky sound while pulling the brass out of the die than you are not lubing the case neck inside properly. This may cause uneven friction at the neck and could throw your case out of wack.

 

[boomtube]

Several things cause bullet run-out, doubtful that a shiney expander can fix any of them.

When some rounds have little runout but others do it's commonly due to poor case necks and no die change can fix that. To "fix" such necks, many of us lightly turn our necks, skimming off maybe 60-80% of the neck circumference just to even things up a bit.

Another common cause of run-out is having too much "bullet tension." Or more accurately, too much difference between the bullet and neck diameter. Any difference greater than about 1 1/2 - 2 thou means absolutely nothing to actual bullet tension but it does greatly increase the required seating pressure. Increased seating pressure almost always increases runout.

The shape of an expander button can increase the rate of bent necks. A long bearing surface, such as what we have in Lee's expanders is best while a "ball" is worse. A ball has minimul neck contact which allows even slight variations in neck thickness and/or hardness to give way a bit more in that spot and that drifts or "bends" necks in that direction, at least somewhat.

Non-concentric sizer and seater dies can do it but since you are getting some good rounds mixed in with the poor ones make that seem unlikely for you.

Bottom line, it's much more likely your's is coming from the cases themselves.

 

[whin4]

Thanks a lot for that.

I don't believe that it's the expander button thats causing the problem as after the last firing I removed the button and ran the neck into a bushing that should give me .002 neck tension.

Excuse my ignorance but if I do try turning the necks would I need to turn the inside or outside or both?

Also, I have not trimmed any of these cases for length as they are still shorter than my chamber. If the necks are out of square could that cause the problem?

 

[elkaholic]

Thanks a lot for that.

I don't believe that it's the expander button thats causing the problem as after the last firing I removed the button and ran the neck into a bushing that should give me .002 neck tension.

Excuse my ignorance but if I do try turning the necks would I need to turn the inside or outside or both?

Also, I have not trimmed any of these cases for length as they are still shorter than my chamber. If the necks are out of square could that cause the problem?

You will need an outside turner. An inside turner will do no good. Hornady makes a hand outside turner that works very well. An out of square case mouth can also cause problems and should be corrected. Good luck......Rich

 

[elkaholic]

Thanks a lot for that.

I don't believe that it's the expander button thats causing the problem as after the last firing I removed the button and ran the neck into a bushing that should give me .002 neck tension.

Excuse my ignorance but if I do try turning the necks would I need to turn the inside or outside or both?

Also, I have not trimmed any of these cases for length as they are still shorter than my chamber. If the necks are out of square could that cause the problem?

You will need an outside turner. An inside turner will do no good. Hornady makes a hand outside turner that works very well. An out of square case mouth can also cause problems and should be corrected. Good luck......Rich
p.s. Try seating the bullets by small increments while rotating the case maybe 6-8 times. This will compensate somewhat for any alignment problems with your dies.

 

[boomtube]

p.s. Try seating the bullets by small increments while rotating the case maybe 6-8 times. This will compensate somewhat for any alignment problems with your dies.

Maybe, it's popular but it's never done a thing for me. Seems that once a bullet starts in cock-eyed it will continue that way. Most seating stems seem to be to loosely fitted to force any significant off-axis correction.

What I've found that does help, some, is to raise the seating stem so high that the bullet is completely contained in the seating chamber before entry starts and then screwing the stem down in small steps until fully seated.

 

[kraky]

You could put that fancy sizing die on ebay and pick up yourself a lee collet die....and most likely watch your problem disappear.

 

[whin4]

After a bit more shooting and a bit more investigation I have found that the problem is with the neck sizing operation. The runout on the neck of fired cases is very good, mostly less than .001. Once the case is run into the neck die ive got between .003 and.006. This is without the expander button.

Am I right in thinking that neck turning wont help this?

Could it be my press that's out of alignment? Any other ideas?

Thanks

 

[Gene]

Good move eliminating the expander ball. That is often the cause of erratic necks. Are you measuring run out off the bullet or the neck? If the neck, that is too much. Run out measured at the bullet ogive will usually be a little more. Suggest you look at the K&M or Sinclair neck turning sets, together with an expander. You simply need to skim the necks, not cutting deep into the brass. If you can keep run out at the neck near .003 consistently, that will work well.

 

[bigngreen]

How far down are you sizing them, I've seen where sizing down to far in one step can cause some serious run out. Look at your shell holder to make sure that is clean also.
Are you tightening the bushing down in the die, if so back it of just a bit so the bushing will have some wiggle room to center up.
That is a lot of run out on a neck, I would be bumming if I was getting that out at the ogive of the bullet.
If it's due to neck thickness variance you should be able to measure it to see how much extra thickness you have in your neck.

 

[Ray Prager]

Howdy .... Just my thoughts , I would shoot those 10 rounds , because they are New Brass ... fire form them .. then see what happens when you reload .
Ray

 

[ODAVID]

When ever I read about runout problems I see actually two separate issues.

A. Bullet run out - Measured on the bullet at the ogaive.

B. neck runout- Measured on the Neck of the brass casing

I feel the less bullet runout the better cause this is how straight the bullet starts out. How ever the neck run is important cause that starts the bullet in the straight direction hopefully if straight.

I would measure the bullet and see how concentric(round) it is. That will tell you what to adjust or replace next.

If you feel the brass neck is not concentric( round) then I would skim trim to even up abit about 3/4 around the brass neck then circular polish with 0000 steel wool then remeasure that for concentricity(round ness)

Hope that helps
odavid