Case neck runout problem?

168bergersapper

168bergersapper

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I've been trying to rectify an issue with neck runout for awhile now. I have fire formed Lapua brass that is fine before sizing. After running through a Redding competition bushing die I'm still getting runout between .0001 and .0008. The one and two thou I'm not so worried about but when I'm reaching numbers as high as 8 thou I'm gettin concerned. I'm using an RCBS dial comparator, RCBS single stage w/RCBS shell holder. Any ideas how I could control this?
 
Try disassembling the die and cleaning thoroughly. There might be some grime around the bushing causing it not to float consistently.

Also examine the brass, the high runout pieces might be different. Thicker necks? Longer case length etc?

Are you using the expander ball? If so, try sizing without it.
 
accumark said:
some times run-out does happen that's why you should use a concentricity gauge which allows you to adjust the alignment. there are a few different manufacturers.
Click to expand...

He's using one, that's how he knows he has runout issues. And adjust what alignment?
 
If you have the FL resizer try it and see what the runout is. I have found neck sizing can do that if you reduce the size by much. When neck sizing you should be reducing dia by only 2 or 3 though.
This is for target sooting.
 
b72471 said:
If you have the FL resizer try it and see what the runout is. I have found neck sizing can do that if you reduce the size by much. When neck sizing you should be reducing dia by only 2 or 3 though.
This is for target sooting.
Click to expand...

This ^

I have an RCBS press and RCBS shell holders. I use a Forster FL die with Lapua brass and seat with a Redding comp die. I either get zero run out or only .0001 that's it.
 
2 things I have found will do this is necks being thicker on one side than the other so skim turning the necks will rectify this and another was work hardened necks never figured this one out.
 
I've also had a bad shell holder. Swapped it out and runout got better.

After switching shell holders, I have also tightened and lubricated the linkages on my press.
 
Thanks for all the input fellas. Yes I've cleaned all the parts of my die in a sonic cleaner and lubbed accordingly. Maybe the bushing might be the culprit. This particular unit was purchased and used to resize for my last batch of brass which was Nosler so different neck wall thickness. Took a measurement of a loaded case (Lapua) and it is .338 the bushing is only .329 so could this be the issue? I've already ordered a .336 from my smith going to pick up tomorrow.
 
With the redding die using expander order a .337 and .336. Do not use the expander in the same operation instead expand on the upstroke of press second op. so a .338 bushing would be required or just buy a lee collet neck sizer so you can control size to where you want .339 step down to .337 then final op with expanderthe sizes will vary with depending on neck thickness will increase with number of firings. Anneal anneal anneal helps consistancy! Sort necks by thickness and if thickness is not uniform you can clean it up with a neck turner or live with it. If you use the expander on the die in the same o it can cause misalignment as the brass is pulled to the top of the shell holder. You also want to keep expanding to the .001 increment more will cause gulling or the need to use lube on the inside of the neck.
 
The bushing has play when you drop it into the die. If you tighten it up it mat be off centre. Leave it just a bit loose and when you have brass in it tighten it up so it won't move and check the con again.
 
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