Concentricity Help on 6GT Brass

[mjwilcox38]

A few weeks ago I posted a thread about run out on my 6gt. Well i narrowed it down to the 21st centry mandrel is causing my run out. It is currently at 2 to 3 thousandths of run out after I used the mandrel. I am using 1.5 under bullet diameter. I an using lube.

Does anyone have any tricks with using the 21st century expander mandrel set to remove the run out it is causing???

 

[rijndael]

Is the mandrel floating in the holder or is it locked down?

 

[mjwilcox38]

Is the mandrel floating in the holder or is it locked down?

floating. It will not lock down.

 

[spife7980]

And that run out is inside and outside of the case neck? Not just outside where your measurements are influenced by neck thickness variations are they?
And it’s there before and after you seat a bullet and not just one or the other?
If you rotate the mandrel in the body, does the run out follow it? If you rotate the body, does run out follow it?

 

[mjwilcox38]

And that run out is inside and outside of the case neck? Not just outside where your measurements are influenced by neck thickness variations are they?
And it’s there before and after you seat a bullet and not just one or the other?
If you rotate the mandrel in the body, does the run out follow it? If you rotate the body, does run out follow it?

I measured inside neck thickness to see of I needed to turn but they were within half thou.

 

[918v]

Try annealing after sizing.