40 years ago,as part of going to the trouble of smoking my case shoulders to see when the made contact in the sizer die,I used feeler gages,and included one in my die box,matched to that die and shell holder.
And,I understand how one can custom taylor ammunition to compensate for a worn gun with excessive headspace,or even one that a poor gunsmith made with excessive headspace .
Its OK if I prefer to use a Wilson case gage with a little granite comparator stand and indicator to do it my way.It works just fine.
I like to use my Starret multi-anvil mic ,with the anvil and clamp removed,to mic the protrusion of the headspace gage.No,I do not shoot headspace gages,but I use them.I strive for just feeling,but not crushing,the "Go" gage.
I have never had a chamber accept a "no go" that I chambered.If I did,I'd set the barrel back and start over.
I am quite sure I can read the drawing,and I am quite sure I understand headspace.
I am sure Mr Bart B,Clark,and AR-15 Barrels do ,too
Mr Guffey,I'm sure you have a great deal of experience,knowledge,and a lot to share.Thank you.
There is a bit of a style issue.It is unnecessary to set on the stool and lecture us about what we don't know.The fact is,you have no way of knowing what we know,therefore,when you talk about what we do not know,you do not know what you are talking about.
Some might find it useful if you would say:
"In my experience,you can use a feeler gage to....."
That would be sharing the gold.
The rant about how dumb everyone is,could be left out.
If I were to make a datum reference bushing to rest on a cartridge case shoulder,I might use a drill to rough the hole,but then I would bore the hole and use gage pins to measure it.
I suppose I could make up a set with tangs on them to mount on my Sylvac height gage,but,I probably wont.It would work good,though.
I do it a little different,but thats OK.