Ok, I found out some interesting things last night. I recieved a Stoney point head and shoulders guage. I measured 20 cases fireformed in my custom built 300RUM. They were all X.X75" to X.X755". I ran 5 thru a RCBS FL die that was 1/2 turn backed out from the shell holder (partial Full Length). This actually made the shoulders grow and would be tight in my chamber. They were all X.X77". That means they grew .002". I ran 5 more thru a neck sizer RCBS die. They did the same. Ok, so I figured I would adjust the die to just full length sizing. This set the shoulder back to X.X735. Only knocked the shoulder back max .002". Which is really where I wanted. Somewhere around .001" would have been ideal.

Tried others in a Redding Bushing die. This was the way to go if you don't have a FL die matching your chamber. Didn't move the shoulder a bit.

Then tried a Browning 308win. Fireformed, they measured X.X43". Ran thru a FL die camm'd over, and it moved the shoulder back X.X39". So either the die or the chamber is not perfect. I finally set up the FL die for Paritial FL. And Got it so it only measured x.x42 on average. I then tried the Lee Collet, and of course worked like a champ on the last 10.

So what I learned was a few things.

1. Neck or partial FL sizing can make fireformed cases grow at the shoulders and fit your chamber too tight and shoulder length can be erratic due to setup. How much you lube or how tight your expander ball can make a difference on how much it pulls the shoulders up.
2. With a custom chamber job or really good headspace job, and a in spec FL die, this works perfect. One or the other has to match each other.
3. With a factory sloppy but inspec chamber, Partial FL can be useful but setup time can be tough and maybe not worth the effort.
4. A bushing die would solve some problems with no expander ball or Lee Collet. Both of these tried did not move the shoulder at all.