Re: Neck turning vs Bullet seating pressure
In my experience with using bushing dies and "no" expander, I've found that if you have, in your case for example a fired diameter of .344" and maybe turned down to 343" for a good clean up, you'll find a .335" bushing will produce a neck diameter of as low as .332" - .333", not the .335" as one would expect.
I got a .335" and a .334" bushing for my 300 ultra, the .334" bushing was sizing them down way too far and is never used.
The .335" bushing was still sizing them down far enough, it forced me to turn the necks unless I wanted to spring for another bushing. I was thinking I'd turn them anyway, but now I had to in order to use the .335" bushing. My necks are .014" thick and I get .002" tension using it now. Incedentally, I get the same tension in my Redding non-bushing FL die without an expander as well, which I had to revert back to useing to elliminate the RO my chamber was producing.
When I used the .335" bushing before turning the necks, which was what I came up with using Reddings "previous" recomendations on how to determine the size to use, I had way over .005" neck tension!
Redding has since revised their suggestion of .002" - .003" under loaded diameter to .001" - .002" under I believe. This still would not have worked on my rifle, the neck of the chamber was so large, .340" -.345" I think. I think .337" - 338" would have been the smallest I could have used.
What happens when you try to step a neck down by the amount a factory chamber forces you to do, is the neck will actually over shoot the I.D. of the bushing (because of the entrance angle) when running it up into it by enough that the spring back is not enough to bring it back to the bushing I.D. the rest of the way up the bushing.
On a tight neck chamber (.002" total clearance), such as the 30/338 Lapua I'm loading for, the case neck will follow the bushing so tight up its I.D. it will actually spring back enough it is actually .0005" - .001" larger than the bushing I.D....
These factors are not really layed out, but the more you use them I'm sure you'll see the close to the same results. Hardness of the necks will vary the sizing of them too, as you might expect.
For a factory cut chamber, as a starting point I recomend a bushing size equal to the loaded diameter of the cartridge, that's for .002" - .003" neck tension.
For a tight neck chamber, .001" smaller than the diameter that would provide your desired neck tension.
I think that's about as close as one can get on the first guess, expect that you may buy anothe bushing if it's a thou off from what you figured.
IMHO, it's a much better representation than simply buying one .001" - .002" smaller than the loaded diameter as Redding recomends, which doesn't take chamber diameter into account at all. [img]images/icons/smile.gif[/img]