Tammons, here's a quick walk through on my process. But before we go any further, I do want to make a point to not use the RCBS neck turning setup. A quality hand held turner is what you want to go with. Sinclair and K&M make nice units. Make sure that you get an expanding mandrel that is .001 bigger than the turning mandrel to avoid overheating and/or galling the inside of the case necks. Scuffed up inside case necks are bad juju for accuracy.
Anyway. here's basically how I do it:
-Take 5-6 cases to use as 'setup' cases.
-Expand with expanding mandrel
-Adjust turner to turn off only the donut while touching as little of the rest of the neck as possible. Make a nice blend into the shoulder. The Sinclair cutter makes a nice transition. I go into the shoulder about .010 or so..just a nice blend so you don't have any severe 'steps' where you stopped cutting. Do this for all your cases.
-Seat a bullet that you're going to work with and measure the outside neck dimension over the pressure ring of the bullet. If you're going to be working with several bullet types, use the one that has the largest shank diameter/pressure ring dimension as you want to have enough clearance to accept the largest bullet you're likely to use. Obviously, you want to seat the bullet so the pressure ring is somewhere in the length of the case neck..not below the neck/shoulder junction, for obvious reasons.
-This case doesn't have the neck turned, so you can now figure out how much you need to turn off to get the final dimension you want. I don't measure brass thickness...all I want to know is what the loaded round measures when the bullet is seated. Set this case aside.
-Taking another 'setup' case, adjust the turner to just take off a small amount of the neck thickness, then seat a bullet and measure. Set this case aside, as you're done with it for turning. You can pull the bullet and use it as a fouler later on.
-Repeat the process with another 'setup' case, adjusting the cutter to remove a small amount of neck thickness.
-Repeat with a new 'setup' case until you get the desired final dimension. Use a new bullet each time you seat a bullet and measure, as the pressure rings are reduced in size when the bullet is pulled and you want to be measuring over the biggest part of the bullet..which is the pressure ring.
Done this way, you can usually hit the dimension you want using just a few cases.
This is just my way of doing it..everyone has their own method. You can click on the 30BR tabs on the homepage here to get some more info on case forming, setup, etc. Make sure and use a decent lube, clean the cutter after each cutting and be really careful if you're cutting the case necks under power as it's very easy to overheat the necks and the mandrel, causing galling and varying dimensions as the heat expands the necks and the mandrel. I do my necks under power and keep a bowl filled with rubbing alchohol on my bench. I set the turner assy. into the bowl after removing the case and while I'm setting the case aside the alchohol cools the turner. This keeps the dimensions the same from case to case.
Just a couple of other things as I'm thinking here..the 30BR's don't have to have tight neck clearances to work well. Just the opposite, in fact. Lots of guys running .002-.003 clearance in these 30BR's. Also, just because the reamer neck dimension is supposed to be a certain dimension..that doesn't mean it really is that dimension. Reamer makers do work to tolerances, so it's best to check the finished chamber neck diameter before you go setting up case necks. This is pretty easy to do, as any reputable 'smith will have a set of guage pins in .0001 increments. You can even run the reamer just part way into a small piece of barrel stub...just enough to get the neck in there..and measure this by insering the guage pins, verifying the exact chamber neck dimension, and proceed from there to set up your case necks, knowing that your figures are exact.
I've done probably 600-700 30BR cases this way over the past few seasons, with some minor changes here and there. Hope this helps. -Al
