U guys are clearly struggling with this one.
Headspace is a nominal measurement. Dies will be a nominal measurement. In the perfect world everything would match but they don't.
When the chamber is being cut the chambering reamer is run into the barrel to a NOMINAL depth. Even headspace gauges vary in length.
It's about managing the headspace u have in your own firearm !!! How do u do that ? I will explain what I do.
I use a Redding Competition Shell Holder Set. These shell holders are graduated in .002" increments. When u begin to Full Length Size ( FLS ) your cases for say rifle/chamber "X" you start with the 'deepest' shell holder e.g. the one that gives u the least case shoulder bump. After performing a FLS on a case, try that case in your chamber by closing the bolt on it. YOU NEED TO REMOVE THE FIRING PIN FIRST otherwise you will be cocking the bolt when u close it and this will seriously compromise your ability to properly feel what's happening. You are trying to feel if u have in fact 'bumped' the shoulder back just enough to allow the bolt to close on that FLS'd case with "one-finger-pressure".
If the bolt is still tight-to-close then pick the next shell holder from the set and FLS the case again, then now try the case again in your chamber to feel if now you have achieved just enough case shoulder bump to get nice easy bolt closing ...........
The whole reason for using the Redding Comp Shell Holder set is that by running the shell holder hard up against the die all the variables of having a dodgy flexy press is taken out of the equation.
A guy of my acquaintance recently had an 'ignition' problem. What was really happening was his shell holder ( the only one he had ) was sizing the case too much. This was not only creating a headspace problem that would likely lead to case separation but the excessive headspace he had created was giving him ignition problems. The solution : tig weld the shell holder up a bit then machine it back in the lathe, to get the right amount of case shoulder bump WITHOUT bumping the shoulder back too far and creating a headspace problem.
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