Yesterday, I bought the hornady overall case length gage, with the modified cases for .257 Roberts and 7X57 mauser.
I have been measuring the oal with different bullets like a deamon in 4 different rifles.
Its kind of fun.
But I must say, one thing I have learned so far is that the method I used for 20 some years of seating long, and then a we bit deeper over and over till the action closes works prety darn well.
The measuring tool is faster by quite a bit, and mabye just we bit more acurate but I doubt if my loads will be any more acurate, or at least very little.
The main value to me though will be with the barnes bullets where seating depth requires lots of experimentation.
...tj3006