Hi Jeff. This should get you started down the right path, although opinions will vary.
I, personally, don't weigh bullets (1,2,300 yd). I use Randy Robinett's BIB bullets. If you are measuring base to tip - they will be off that much, but that length is not important. What is important is base to ogive. If you buy quality bullets, then you don't have to measure this on each bullet either. In short - trust Randy or any other fine bullet maker.
Your brass will "spring back" different amounts based on work hardening of the brass, so it is hard to determine what your chamber is from that. This is where annealing comes in, but that is another post. Ask the gunsmith, that made your rifle, what your actual neck was reamed to. They will have the tools to measure this. If that is not an option you can make your own chamber cast. I have never done this, so can not comment on how that works.
I like at least .002 total clearance to .004 clearance. As long as all my cases are the same, anywhere in that range I feel the cases are good to go. Once you get your over bullet measurement, start with a bushing .004 under that. That will give you .004 neck tension. For example; Let's assume you have a .330 neck -if the neck, with a bullet in it, measures .327 over the pressure ring that would give you .003 clearance. I would start with a .323 bushing (.327-.323 = .004 neck tension) You will get lots of different opinions on this paragraph.
As far as case length: Lets assume you have a 1.520 max case length. I would trim them anywhere from 1.500-1.505 (again as long as they all are the same in that range) Whenever a case would get to 1.510 I trim all of them. I check the case length periodically. They almost always measure within .002 of each other. Any more than that, I would trim them all to the same length (see Jack Neary's You-Tube videos) If you only bump your shoulder back .0005-.001 you won't have to trim very often.
Hope this helps. As stated earlier, opinions will vary. Gather as much info as you can and then start to develop your own system. If you want good reading go to 6mmBR and look up 30 BR. You will see lots of good information that has withstood the test of time.
Stanley
