You are confusing headspace with the dimension that
controls it. eg. New York and Chicago are 800 miles
apart, but their locations are defined relative to
Greenwich England. Headspace (not a suprise) is the space
the case head has. All the man wanted to know was if the
gun was safe to shoot with that brass. He said he didn't
have access to a guage. Finally you are measuring clearence
period. When the chamber refuses a no-go the clearence has
reached zero. The system I gave is safe, and will work for
any cartridge no matter how odd.
Good luck!

Thank you all for your comments. They have been helpfull.
Still I have a question:

Since headspace is a defined nominal measure with minimum and maximum tolerances allowed for a given chamber and clearance is the actual 'space', determined by the combination of headspace and tolerances in cartridge measures, isn't the actual clearance in a chamber-cartridge combination much more important than the question whether only headspace is within limits? So shouldn't reloaders be more concerned about proper clearance?

If so, What are the tolerances for proper clearance?


'The only way how to learn to shoot is to shoot more'

It can be both, what Irv has said and what you have reiterated. You have described the technical term, Irv has described the practical explanation.

Look here, or here, or here. Lots of different approaches to the same thing.

cheechako; Too bad you didn't read what I said before replying. "Scotch" tape is a hard clear tape. It is not
"masking tape". That is your first problem. I said to stick two layers together (to keep your Mike clean) and measure them. At this point I will have to help you, the tape thickness is one half the mike reading (about 0.002).
If you try this please do not force the bolt, just feel for the shoulder. For safety take the firing pin out.
Now to know the clearence between the case head and the breech it is necessary to count the layers of tape and multiply by the thickness.
The guy wanted to know how to measure "headspace" without a guage in order to check a particular cartridge in his gun.
I stand back of every word I have said.
Good Luck!

Headspace is the distance from the face of the breech to the cartridge base ( it is clearence)period.
Take a new commercial cartridge and add layers of tape to the base until you can just feel the shoulder touch as the
bolt starts to close. If you take the firing pin out it will
be much easier to feel. Pull the bolt and place the case under the extractor. To measure the tape stick two together
and use a Mike. This will give the headspace with that case.
Good luck!