neck runout??

[444marlin]

I just received a concentricity tool and neck turning lathe from 21 century,very nice stuff.
What I found is that my fired brass,all winchester out of three different 25-06 had runout from .002-.006,I still have some runout after turning the necks,but the wall thickness is less than .0003.this would seem to indicate that the case is out of round.I use redding competion bushing dies so it not caused by the dies,I was unable to measure the runout on the new brass as I never had the tools yet.Do you think it is the winchester brass? What would be you guys thoughts on this?
Thanks Wayne

 

[Zia Hunter]

I have similar experience with Winchester brass and generally wind up culling a fair amount of new cases due to neck wall variation. Neck turning will help but if the neck wall thickness in single case has a significant amount of variation, nothing will cure it. For plinking and fun shooting probably not an issue but if you are reloading for accuracy it will be. The neck wall thickness you mentioned does not seem right. The Winchester cases I have reloaded have neck thickness in the range of .013"-.014". What are you measuring your neck wall thickness with?

 

[444marlin]

yes my necks are .012-.0135 before turning,and after turning to clean finish .011.But the runout is still there even though the wall thickness is excellent.

 

[444marlin]

I just received a concentricity tool and neck turning lathe from 21 century,very nice stuff.
What I found is that my fired brass,all winchester out of three different 25-06 had runout from .002-.006,I still have some runout after turning the necks,but the wall thickness is less than .0003.this would seem to indicate that the case is out of round.I use redding competion bushing dies so it not caused by the dies,I was unable to measure the runout on the new brass as I never had the tools yet.Do you think it is the winchester brass? What would be you guys thoughts on this?
Thanks Wayne

I should have stated .0003 devation in wall thickness after turning,which is very good

 

[savageshooter86]

my necks are within 0.001" but it is a 308win. Nothing done to necks except sorted by neck wall thickness. Use a Lee Collet Die then runout stays same or gets better.

ZiaHunter what cal you shooting? My neckwall thickness is same as you 0.013-0.014"

 

[Zia Hunter]

The Winchester brass I was referencing was in 220 Swift and 308. The variance after turning of .0003 is very good but .011 neck wall thickness is pretty thin especially for a standard chamber. Try FL sizing the brass with a body die and then neck size then check concentricity. If you are shooting a bolt gun, the fired cases should be concentric and show very little if any variance.

 

[fdshuster]

Wayne: All brass will have variations, even Lapua, although a lesser amount than Winchester. Gotta be from the time the brass was formed.

Most will straighten with the first firing, some will never straighten no matter how many times fired.

As an example, I have many box's of 20 Lapua's in 220 Russian, 6BR, 223, 308, etc., and the majority will have at least one (maybe 2), that will have consistant R/O of as much as .004". 220 Russian (now 6ppc) and 6BR's have been outside neck turned, does not matter, the R/O continues.

Bought a bag of 50 Winchester 308, loaded them & R/O was minimal, fired them, reloaded and not one had R/O of more than .002" and that was only a very few. Quickly went back to the store to buy more (Cabela's), but the lot number was different. That bag of 50 was mediocre, at best.

Outside neck turning will not eliminate R/O if it's caused by mis-alignement between the case neck & shoulder, and/or the shoulder & case body.

I mark the problamatic cases & keep them for short-range, first round fowlers & informal, not match use. Actually under those requirements I've never seen any lessening of accuracy.

 

[444marlin]

Thanks for your help,I never ran them in the body die after firing.It sounds like this may be common.I just tried some once fired 300 wsm winchester and they were quite a bit better.
Just to try I may get some lapua 30-06 and neck it to 25-06 and see what happens.
My target 25-06 rifle shoots one hole about .500 edge to edge,but often I will get one sometimes two on the edge of the group(five shoot groups) they chrono very good.

 

[BoydAllen]

I think that Winchester brass may be harder and springier in the neck and shoulders, and that if you want to do a little experiment you may see a difference by annealing some, not a full anneal, but what may be referred to as "stress relieving" or what amounts to a partial annealing, that leaves cases with a useful amount of neck tension/bullet pull. If you decide to do the research ( on how to do the annealing) and annealing, please return with your results as to fired neck runout.

 

[444marlin]

Wayne: All brass will have variations, even Lapua, although a lesser amount than Winchester. Gotta be from the time the brass was formed.

Most will straighten with the first firing, some will never straighten no matter how many times fired.

As an example, I have many box's of 20 Lapua's in 220 Russian, 6BR, 223, 308, etc., and the majority will have at least one (maybe 2), that will have consistant R/O of as much as .004". 220 Russian (now 6ppc) and 6BR's have been outside neck turned, does not matter, the R/O continues.

Bought a bag of 50 Winchester 308, loaded them & R/O was minimal, fired them, reloaded and not one had R/O of more than .002" and that was only a very few. Quickly went back to the store to buy more (Cabela's), but the lot number was different. That bag of 50 was mediocre, at best.

Outside neck turning will not eliminate R/O if it's caused by mis-alignement between the case neck & shoulder, and/or the shoulder & case body.

I mark the problamatic cases & keep them for short-range, first round fowlers & informal, not match use. Actually under those requirements I've never seen any lessening of accuracy.

I did more checking and sat back for a minute and it is the case just ahead of the web where the body die does not size,it is like a small bulge,but when you dial the neck at that distance from the support it gives you that high of a reading.the support rollers on the concentricity gauge are where the small bulge is.
so your post is absolutely correct.