Originally Posted by gwtx
I have the mention somewhere on this forum about FL sizing without the expander, then neck sizing with a collet(lee?) die. Is there any significant advantage ? Gary
sorry, I found the threads I was looking for.
Actually if you FL size without the expander the neck is also sized. You need to "open" the neck back up as most sizing dies squeeze the neck down way more than needed.
You can open the neck back up a couple ways. Put the expander back in the die and expand the neck from the top down as opposed from the inside out as with normal sizing.
You can use a Lee Collet die and just shove the mandrel into the case mouth, or you can go through the complete neck sizing motions and run the case into the collet die all the way.
My favorite way to do this is to use a Lyman "M" die. It opens the neck back up nicely and you can apply a slight flare to the mouth if desired.
The theory behind all of this is to keep bullet "run-out" to a minimum. Run-out can be caused by several things and the biggest cause is the expander button. When the expander is pulled back through the neck it can and does pull the neck off center just a little causing unwanted run-out. Expanding the neck from the top down helps eliminate these crooked necks.