Chasing around looking for the exact headspace in my rifle, I happened upon an RCBS Precision Mic. tool (Correct calibre) used, for a tenner (usually around £65). I simply cannot understand how it measures! Yes I can see the marks, but no dimension seems to tally even closely with my other guage.
I had also done the usual thing & bought a Hornady Headspace Guage with the correct bushing & taking a fired case did the measurements on a number of cases, then selected a mean average. In my case, 2.049".
So, I set me F/L sizing die using an 'O' ring enabling me to get finite adjustment to size to 2.048".
Then, just to see where I can get to in terms of + tolerance, I start measuring using rizla papers at the cartridge head (base) and measuring from the shoulder datum point including the paper (Not successful so I started using kitchen foil cut to size) and I get to 2.0515" headspace measurement.
this gives me a go/no-go dimension.
So a question: What actually is my actual headspace?
Is it a) the fired case average dimesion 2.049"?
or b) the final 'go' dimension lets say 2.051"
Adjusting my sizing die to size brass at 2.051" will ensure the finished cartridge chambers and fires in my rifle. Is it likely as a result to be more accurate by a degree or two?
or is it just easier on the brass?
Is there anyone out there able to enlighten me further please?