What is acceptable neck run out??


May 17, 2005
I'm doing some loading for a friends .270 win he bought new RCBS dies and I FL sized all the new winchester cases he bought before loading. I cleaned / polished once fired brass and sized. On a whim I ran some thru my RCBS Casemaster to check neck run out. On about 90% of the fired / sized cases the neck run out was .004". I checked to new but sized brass and most of it was .002" or less run out with maybe 25% .004" or more. So then I took 3 cases that had been fired in his rifle, cleaned them measured neck run out before sizing, less then .002" most @ .001" took out expander / decapping stem and ran them thru sizer die, all were at .004" run out. So my question is , what is acceptable neck run out on hunting ammo and should I have him return these dies for new ones. Or is then some other way of checking to see if its the dies or something I'm doing that is causing this. I did clean the sizer die good today to make sure nothing was in there, i.e. lube build up. Any thoughts.
Have you squared the die to the ram? Try setting the die with it just touching the shell holder and locking the die in place with a bit of pressure on the bottom of the die. There might be some play in the threads of either the press or die that`s allowing the die to slightly tip.
That is more than acceptable runout. I believe acceptable varmint load runout is .005 or less....I think!
Both the replies you have gotten so far are right on the money.

I would make sure you have the die squared with the shell holder just to be sure that is not inducing the run out.

But, I doubt if a runout of that magnitude will make any difference in hunting rounds. If you were shooting bench rest or long range varmints, maybe. But on a hunting rifle, I do not imagine you will be able to tell the difference.

I did measure a couple of cases for run out picked some with .004" or more and set dies as suggested, marked the highest point on neck ( where i got the highest reading ) and then ran thru the dies again, each time turning the case a 1/4 turn to see if that would help with run out, i did notice a small difference but less then .001" improvement. I will shoot the loads I have loaded and before resizing again I will adjust the dies as suggested and see if run out improves. RCBS Casemaster instructions suggest .002" or less is acceptable and to set aside any cases over that, to be honest I do not as a matter of course measure run out on loads I do for hunting rifles, but in this case I am looking for best load for this .270 win so figured I'd check. I am also loading some .30-06 loads for another buddy and checked run out on his brass after sizing and find most are .002" or less. These are my RCBS dies.
Thanks for the info and I'll check my set up as suggested. I figure its most likely human error but you never know.
If you are looking to get the least run out, you will need to turn the necks so that neck thickness is out of the equation.Rick.
I checked neck thickness on most of the new winchester brass and it ran .001" or less difference, would not think that would account for most cases being .004" run out. So question, if I buy new dies set them up for the rifle I'm looading for as to depth so I just size shoulde back say .002" or so and then tighten lock ring and set screw in lock ring, do I need to have ram up when i install dies in press each time or can i assume they are straight after set up. I like to set my dies to just set shoulder back requried amount , could i be introducing run out by just putting set up dies in press and tighting them down to lock ring after first set up?
The cases are coming out of the rifle with 0.001 runout and then go to 0.004 after sizing without the expander ball. That indicates some misalingment in the system. One problem with screwing the dies to contact the shell holder is the possibility of pushing the shoulder to far and overworking the brass. I think a better solution would be the Redding competition shell holders. They have a 0.002" difference in thickness so you can control the shoulder set back. Another commonly used method is to use shim stock under the lock ring. If you are using the same press/shell holder for the 30/06 and 270, that indicates the problem is confined to the die or the lock ring. Did you use a ball micrometer to measure the neck wall thickness?Rick.
I used RCBS Casemaster neck for neck thickness, not sure if its as accurate as ball micro but seems pretty accurate once you get used to it. Need to be consistant with holding case.

I must say I've gotten some good ideas from all the responses and will go back to square one and re-set dies again, then check all the possible causes as I re-size the brass.
Also, with all my dies I used fired cases from the rifle I'm loading and get headspace of fired case then adjust dies to set shoulder back .002" for hunting ammo. There in may lay the problem, if the ram of press needs to be up and putting pressure in die to get square to ram / shellholder and I'm screwing in die to adjust the right amount of shoulder set back I don't have pressure on die from ram, also I notice if I set the die and tighten lock ring and set screw and then back off the lock ring the set screw does not always remain tight against the threads of the die, I tightening set screw with die and lock ring loose is not a good idea possibly.

We may be beating a dead horse here, I did get one load .207 win, H-1000, 140 gr. AccuBond to shoot 3 shots @ .410" so I am loading that load again with brass less .002" run out and then with the brass that is .004" to see if there is noticable difference. This load only produced a little over 2700 fps and I'd like to get more but it looks good on the target.
If you have not yet tried IMR or H-4831 in the 270, you should try them. If you ever decide to get another press, consider the Forster Co-Ax. You don't have to screw the dies into the press. The lock ring is pushed into a slot in the press. Changing your dies is a pull out/push in. The dies have some movement when in position which helps to self center the die and case. You may want to consider the Redding competition shell holders or shim stock to aid in the amount of shoulder set-back.Rick.