Skim Turning Necks?

[PatMiles]

For some reason in the back of my tiny little mind I seem to remember a post that told of brass imperfections on the inside of necks being pushed outward when an expander ball or mandrel is run through the neck. If this is true, would skim turning the necks after using an expander ball or mandrel true up the OD of the neck so the imperfections don't get pushed back to the neck ID and cause seating pressure variations. I have 200 new Lapua 6.5 CM pieces of brass to prepare.
TIA,
Pat

 

[Richard Coody]

For some reason in the back of my tiny little mind I seem to remember a post that told of brass imperfections on the inside of necks being pushed outward when an expander ball or mandrel is run through the neck. If this is true, would skim turning the necks after using an expander ball or mandrel true up the OD of the neck so the imperfections don't get pushed back to the neck ID and cause seating pressure variations. I have 200 new Lapua 6.5 CM pieces of brass to prepare.
TIA,
Pat

exactly

an interesting observation on my part. take a bushing sized piece of brass that hasn't been neck turned and check it with a quality concentricity gauge like the 21st century. then run that same piece of brass through an expandrel mandrel and check it again.

no doubt you will be suprised what you find.

 

[DMascari]

You are correct. It's a good idea to turn brass to clean up the high spots.

 

[Shynloco]

You are correct. It's a good idea to turn brass to clean up the high spots.

Yes, but run it through an oversized mandrel die before turning the outside. I've tried turning both the inside and outside of the necks of brass and reaming the inside is nothing but a waste of brass and effort. The oversized mandrel with take care of pushing the uneven thickness outward and then turning the outside evens up the brass thickness and gives good concentricity runout.

Alex

 

[gotcha]

For some reason in the back of my tiny little mind I seem to remember a post that

Your "tiny little mind" is working just fine.

 

[jr600yd]

The short answer to Pats question is YES!