So I have read that for the bushing dies, you size the bushing 0.001-0.003" below the diameter of a loaded round. The neck on my 6mm BR rounds starts at 0.266 at the mouth of the case and goes up to 0.270 just before the taper. It is 0.268 in the middle. I was going to pick up some bushings sized 0.267-0.265. Am I off the mark or should I work with the smallest diameter of the neck.

I am not sure that is the right way of doing it.

Theoretically, yes, but you do not know the actual chamber neck.

If you have a tight neck rifle, the neck diameter should be on the barrel.

If you don't, here is what I would do.

Measure the neck thickness of your brass.

Let us assume you get 0.012"

Double it, and add the bullet diameter.

This should give you 0.267"

You should use a button that is 0.265" or smaller.

The Redding bushing die FAQ states that if the neck thickness varies .002 or more to use the expander that comes with their die. And let the expander set the final inside neck diameter.

Bushing dies work best with neck turned brass in tight neck chambers. And if you do not neck turn and do not use the expander the inside neck diameter will vary .004 and taper to the base shoulder junction.

If you do not plan to neck turn I would not bother with a bushing die with brass that varies that much in neck thickness.

Thanks guys. That should be a good place to start.