Re: Neck Sizing .300 Rum (any issues)
I can tell you that if you move the shoulder back too much you WILL have major problems such as stuck cases and even split cases. If you dont move the shoulder enough, after a while the become sticky as well.
IMHO the best way to deal with the 300 RUM case is to get a body die which doesnt touch the neck and set it to bump the shoulder .0005 to .001" back. This will also shrink the diameter of the shoulder area a tad. Then neck size. You will maximize the life of your brass this way AND have very reliable/smooth feeding and extraction.
You may be able to neck size only for a couple of firings. It will depend on the quality and demensions of your chamber AND how hot you run your loads. When they start to extract and chamber with some resistance, then it is time to run them through the body die.
It may take some trial and error to figure out what works best for you but definately DO NOT use any cases who's shoulders get bumped back too much. IMHO .005-.006 is way too much in a 300 RUM. Keep the headspace close and things will go smooth. The larger the headspace of the rifle, the more you bump the shoulder back the more compound the issue. The tighter the headspace is, the less critical and more forgiving it seems to become.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.