Question: If I use new brass with the false shoulder as described can I load those brass to my regular charge and use them to shoot groups or should I just use a light load to fireform them ?
Also should I false shoulder /fireform each brass or just a couple of them and set my die on those for the rest ?
Sorry for the questions but still learning some of these finer points about reloading.
What you are trying to achieve is a "tight fit" of
your brass in
your chamber - from
your bolt face to the shoulder in
your chamber. No manufacturer anywhere will be able to precisely replicate your dimensions - all is done to plus or minus tolerances, not absolute sizing. So, if you want that exact fit, you need to do the re-sizing thing with each of your brass. And you wipe out all that work, if you just "normally" re-size hard onto the shell holder the next time.
So, for range use, on paper targets, most people appear to be satisfied with a bit of pressure to close the bolt - a tight fit of brass to chamber. Most hunters, like me, do not want that - as most of us have missed occasionally, we want a very quick re-chamber for a second go at it - that often means we do NOT want any resistance on the bolt closing, even if that means some degree of loss of exact precision - which might be actually "real" or not depending on your abilities and the rifle's abilities. In my experience, my "best shot" is the first one - after that, I am behind and trying to catch up - game is likely moving, more difficult to hit, I am getting frustrated and so on. All that stuff takes away from "precision".
So one way to do this is to go through the fitting part until you get the die creating the false shoulder exactly where the bolt closes with "some" closing pressure. Now take a feeler gauge or whatever, and figure out what clearance existed between your shell holder and the bottom of your die, at exactly that point. Write that down somewhere - chances are good that is where you want to be able to reset that die in the future, for the next reloads. Might want to add a thou or two to that number to make "hunting loads" - will get you not much or no bolt closing pressure. In my experience, a concern about brass longevity is a target shooting thing - I doubt 50% of the brass that I have fired at game was ever looked for - just not important at the time. Of course, one shot fired and game down before cycling bolt - I do put that shell casing in my pocket!!!
I hunted white tail and mule deer with Ruger #1 in 7x57 for about 20 years. Basking in 12 or 13 "one shot" kills in a row. Then, between previous evening's Jack Daniels and other factors, a memorable mule deer buck took 9 or 10 rounds fired by me before he quit - I think, over the course of several hours, I hit him twice - first shot, and last shot. So, quite a pile of brass from the first run of "hunting brass" - I think I only have the last one fired from that mule deer...