Excellent explanation. I've always wanted a more detailed explanation and this thread hit the nail right on the head!
I am just about ready to load my first,,, I think. Something always comes up new that I need to know more about before I start. Now I am waiting to get a case re-sizer because all the brass I have collected over the years (shot only once, some twice) are different length, from 2.484 to 3.000 and the Nosler book says max is 2.494. Now mw0428 says we don't need to length size them??? We both have bolt action 30-06. Mine is a very old BSA? and hers is new Mossberg.when you 'full length' resize a shell, you stretch the shell FORWARD, cause thats the only way it can go; the brass thins as is it stretched and gets longer, causing it to get thin; then you get split cases, due to pressure more than the thin case can take; and you also end up trimming them for being too long;
The above mostly applies to autoloaders;
If you shoot a bolt action, or lever action rifle, dont full length re-size your cases;
just collet size them for the neck size of the round you are shooting; you have a perfectly sized shell for your rifle; and your cases will last ten times longer;
From LEE 2ND EDITION RELOADING MANUAL
New here. Just been looking around. Been casting bullets and reloading for over 50 years. Rifles, pistols and shotguns. I am impressed. You guys rock. The explanation of headspacing was better than very good by all. For the newbees here you can't go wrong, listen up. These guys know what they are talking about.