Neck turning

[Jeff Von Rosenberg]

I have tried every thing, but I found this. If I turn fired unresized cases I get necks to within a half thou. of neck thickness but if I turn fired cases that have been resized and run over an expander mandrel they come out egg shaped after turning.I have already ruined about 50 cases trying to figure it out. I even put the indicator stem inside the case neck to check concentricity and they were good(.001) untill I ran them over the expander mandrel and turned them, then they got worse. Even tried putting expander die in different press and tried a different expander die with same results when turned.It also seemed to work fine on new unsized cases, turned to within half a thou.Problem is this is a 22-250AI and I have about 300 cases and 200 of them have already been fireformed and resized . The others with nothing done but removing primer after fireingturn fine, but the expander mandrel does not touch when trying to expand,but they turn within 1/2? Thou. I m confused HELP!!! I'm using a 21st Century case lathe and expander die, as I have for several years with no problem.

 

[LCazador]

Are you using a bushing die for resizing? Sounds like there is something going on with expander. Did you check expander dimensions, is it concentric? Does your die have an expander?

 

[Jeff Von Rosenberg]

I have a regular die for sizing before turning as a bushing die does not size the last 30% of the neck. I use a bushing die after necks are turned. I have checked my expand real mandrel and it's concentric. I don't use an expander ball in my dies.

 

[dkhunt14]

Could it be that your regular die is too big in the neck area that it is not making the case small enough to use the expander? Sometimes with a turned case I have seen guys turn them too thin; that a regular die won't squeeze them down enough to hold a bullet. Then they have to go to a bushing die with a smaller bushing to get any tension to hold a bullet. Matt

 

[Jeff Von Rosenberg]

No the ones that have been resized with that die are the problem they are small enough that they expand with the mandrel. The crazy thing is the fired cases that haven't been resizes or expanded turn fine as new cases do however new cases must be expanded but they turn fine after being expanded. I know it's confusing.

 

[BaconFat]

Is it possible that the expanding mandrel is not perfectly square to the case neck. So instead of your mandrel being perfectly vertical at 90 degrees from horizontal, it's off by a degree or two. That sort of an alignment would cause your case neck to form in a slightly oval or egg shape opening. Did you check the neck concentricity before and after running a piece of brass through the expanding mandrel?

 

[artbosco]

I have a regular die for sizing before turning as a bushing die does not size the last 30% of the neck. I use a bushing die after necks are turned. I have checked my expand real mandrel and it's concentric. I don't use an expander ball in my dies. Smart move!

I'm going to assume you're necking up new brass since you say you're using and Expander Mandrel prior to turning.

If that is the situation, there is No NEED for two separate F/L dies.

Prior to turning, take the bushing out of the F/L bushing die so that you just push the shoulder back. No lube required when you do this. Adjust as necessary, in order to push the shoulder back .001" to .0015". Chamber the case with the firing pin out of the bolt to ensure that it will chamber. Expand on a mandrel made by the same company who made your turner [very important]. Turn.

After turning and arriving at the OD for your loaded dummy round, put the bushing of choice back in your F/L bushing die, lube your cases and resize with the F/L Bushing die.

 

[BoydAllen]

You say that your necks become egg shaped. How do you determine this? Also, when you say that your turned necks are within a half thousandth are you referring to variation in neck thickness (For this, that is quite a lot.) or concentricity? When you use an expander mandrel, do you lube the inside of the case necks, and run the mandrel in slowly?

 

[mikecr]

You're seeing the very reason it's best to turn NEW brass.
It sounds to me like your FL sizing of the fired necks isn't working out so well.

 

[Jeff Von Rosenberg]

I believe you are spot on as usual Mike!

 

[BoydAllen]

A little detail that may have escaped you about sizing the fired brass before turning is that if you remove the expander in the die, and then do all of your expanding with the expanding mandrel/die setup, assuming it is a one piece die, your cases will probably end up straighter.

 

[Jeff Von Rosenberg]

Yes I don't have expander balls in any of my dies.