Belted mag cases "only headspace" off the belt for the first fireing, "IF" you DON'T push the shoulder back when resizeing!!!

As for neck sizeing with a FL die. I like to back the FL die OFF the shell holder one full turn. I then take a blk magic marker, and blacken the neck and shoulder of my case. Then i lube the case and size it. Now i look at how far the case was sized on the neck. I ajust the die untill i "just" size the neck, but NOT touch the shoulder!!! Once done, i try the case in my rifle and see that it chambers "ok". If it doesn't, turn the die IN 1/4th turn, size it, and try again!!!! Continue untill it's where you want it....

This works on ALL bottle neck cases.

Hope i explained it well enough for you to understand!!

Drilling Man