Ill pick one of those up but what about the other method of chambering a fired formed case thats too tight for the chamber. Why is this not happening with my gun after three firings?
If you are doing what I think you are doing, you set up the die like the typical manufacturer's instructions. That is, you have the shell holder pressing against the bottom of the die at the top of the ram stroke. When You size your brass, you are shoving the brass into the die till the shell holder touches which is both sizing the brass right down to the belt and bumping the shoulders back so the case is within SAAMI dimensions when you pull it out of the die. In other words, it's not happening because you are sizing the whole fireformed case back to dimensions that guarentee it will fit in the chamber.
If, after you get your new Hornady Headspace measuring tool (which only measures headspacing for non-magnums), you back off on the sizing die and adjust it to "just" bump the shoulders back .001" or .002" you may see some hard chambering brass. The belted magnum cartridge was designed to headspace on the belt. Standard bottleneck cartridges headspace on the shoulder. By backing off on the die what you are doing is changing your brass from headspacing on the belt to headspacing on the shoulder.
Another very useful tool is the RCBS Case Master - it allows you to measure case wall thickness just above the base where it thins as the case is used more and more. It has a long arm with a bent point on it that allows thickness measuring all the way down inside the brass. Measuring the case thinning you will see a dip in the dial indicator needle as you pass over the ring where it thinns.
The reason for measuring this is this is where the case does most of it's stretching which causes thinning. The case fails if it gets too thin. There is a good explanation of the phenomena here with analytical animations showing the stretching phenomena:
Rifle Chamber Finish & Friction Effects on Bolt Load and Case Head Thinning Calculations done with LS-DYNA
He doesn't use a belted magnum case but the belted magnum acts just the same.
Since reading his WEB page I measure all my rifle brass to see if there is thinning going on. When I see the needle "dip" more than .003" I discard the brass. The .003" dip wasn't anything scientifically derrived, I saw the dip, fired the brass once more, it didn't come apart but the dip increased to .005" and I wasn't about to shoot that brass, so I decided .003" was "my" limit for considering brass good enough to shoot. YMMV.
It makes a lot of sense to keep brass together in batches segregated by manufacturer and number of firings. Knowing the brass history and paying attention will get the most life out of the brass with safety.
Edited to add:
All that said, right after writing the above I got out my brand spanking new 7mm Magnum RCBS competition die set, the set with the full length sizing die and micrometer seating die, my feeler gages, digital calipers, Hornady headspace comparitor and got ready to spend an hour adjusting the full length sizing die to bump the shoulders .001" to .002".
Using the "E" bushing I took a fired and deprimed (but not sized) brass. Put it into the E-bushing in the calipers and set the calipers to read zero on fired brass. I did that for 5 as fired cases and they all read the same plus or minus .0005". Then I set up die per the manufacturer's instructions - that is with the case holder pressing "tightly" against the bottom of the die at the top of the stroke. Ready to begin the adjustment process, I lubed and sized the first case, wiped it off, put it back in the calipers and by golly it measured -.002". So I did another one. Same result. Third one measured -.0015", and so forth. I was ready for a session trying to get the die to bump the shouldera .001" to .002" and by happy coincidence it bumped them for an average just under .002" all on it's own adjusted per RCBS instructions. I LOVE IT when that happens!
I tightened the set screw to freeze the lock nut, tried one more, same result and concluded this puppy was adjusted. Time to go load some ammo.
That doesn't happen often, in fact it's the first time it's happened to me, but every now and then there is a happy relationship between the chambering reamer used by the manufacturer of the rifle and the sizing die.
But it happened this time. I'll take it!
Fitch
