Originally Posted by mathman
Originally Posted by gzig5
Pull the expander ball out of the typical FL sizer and you'll find your neck being squeezed down 8-10 thou at least, from fired diameter. The ball pulls it back out to a larger diameter There is usually more than enough to compensate for a couple thou taken off by neck turning. In fact, turning will make the brass last longer because it's being worked less each cycle. Most FL dies are pretty tough on brass.


I don't believe so. The cycle is the difference between fired OD as determined by the chamber and sized OD as determined by the neck section of the die. A thinner piece of brass interacting with the expander ball just shifts some of the cycle away from the expanding portion onto the firing portion of the trip.

I mentioned the thinner brass often working better viewed from a straightness/concentricity viewpoint.


I guess the way I look at it the smaller OD due to neck turning results in a larger ID after it is sized down and before it goes back over the expander in a standard FL die depending on amount of material removed. In my mind that expander will move less metal as it comes back through, thus "working" the brass less. Due to difference in springback, your final ID and thus neck tension may not be the same as before. But in my experience, most of my FL size dies go way beyond what is needed when sizing brass down, most likely so that they will work with all the different brass available. For instance, working with a 22BR now and the Redding FL die I have has a neck diameter of .240 and the Forster about .242. The bushing I need for the Type S neck and FL sizers for proper tension with uncut brass is .250/249". So the necks get way oversized than really needed and then pulled back out by the expander ball. That .010" sizing difference each time is much greater than the case to chamber neck difference for growth during firing and has a larger influence on case life in my opinion.

Last edited by gzig5; 12/18/17.