Originally Posted by bigbuck
How do I know and measure my shoulder to see if it is set back to far? What kind of tool do you use?
I use an RCBS Precision Mic. Hornady and others also make tools that does the same thing.
Fired cases are put in the tool and the case headspace (head to shoulder reference, or datum) from case head to shoulder is measured. After full length sizing, the sized case is measured to see how much shorter the case headspace is.
Any more than 2 thousandths shorter is too much. You'll get a 1 thousandths spread across your cases if they're lubed uniformly. Other wise, too little lube results in not enough shoulder setback and to much lube lets the shoulder get set back too far.
Redding sells shell holders in 2 thousandths steps over the standard so one that lets your die just touch it at the top of the ram's stroke will result in uniform fire case head setback.