I'm prepping some 300RUM Rem brass right now. The 300RUM Rem brass I've used takes some work to prep. Neck thicknesses are quite variable and theoretically, the bullet release at firing will be more variable with variable neck thickness. I set the neck turning tool to .015 (this is for .308--might be thinner for the .338 EDGE due to being necked up) neck thickness as this generally leaves 60-80% of the neck turned. This is for a factory rifle/barrel and so I don't want to turn any more than necessary as the neck area dimension of the chamber is larger than I'd like it to be--don't want to work the necks anymore than necessary from firing to sizing. The 60-80% idea on factory barrels I picked up from Sinclair's book.
What is the neck dia. of your brass after firing or do you know the chamber dimesion at the neck? With a custom chambering like that your 'smith may have a preferred neck thickness. You just don't want to turn off too much--only as much as needed. Hopefully, you'll be able to get the case necks fairly uniform while not having them expand too much in the chamber and get end up getting some brass hardening issues. Can always anneal, however, if you start to split necks. Some chambers are 'tight-necked' on purpose and the brass has to be turned to fit in the chamber.
Haven't used an inside reamer. That's a different animal. Just used the Sinclair neck turning tools.
If you already know this stuff, I apologize. Just when turning necks, you want to have a good idea of the dimensions involved and why you're doing what you are doing.
I've seen Carlock reccomend Redding Dry Neck Lube as well. Trying it right now and hoping to see if there's any difference over the chrono here soon. Might help the bullet release be more consistent. After priming, dip the case neck in the media a couple of times and then wipe off the exterior. Who knows--might aid in consistency.
Good luck.
