Head space and the RCBS Precision Micrometer

BadMatrix · Nov 19, 2022

I am trying to wrap my head around Head space and if after the whole process, is this a number or setting unique to each rifle:

I have everything in order with the factory fire formed cartridges.

I have a question for correctly reading the measurements on the Precision MIC for .308.

The body has a scale with each body mark 0.050 as follows: 0.0,0.050, 0.001 and so on.

When taking a head space reading, will the headspace nut always align with the zero line on the body?
If not, if the nut stops on lets say at 5, and the scale on the body is lets say 1.5 is the measurement then 0.0065?

NikA · Nov 19, 2022

I don't own this tool, but I did read the instructions to attempt to answer your question, since I have a fair amount of experience using micrometers.

I would say that of the headspace nut is far off the zero mark, you've either got the incorrect model or something is far off about either your firearm or measuring method. Based on the instructions and the limits of typical headspace, your measurement should be within 10 markings on the nut of the zero mark (0.010").

Each full revolution of the nut is 0.050" based on the product pictures I see online. If the body stops at 1.5 and the nut is aligned at 5, the measurement would be 0.155".

Hope this helps.

BadMatrix · Nov 20, 2022

NikA said:
I don't own this tool, but I did read the instructions to attempt to answer your question, since I have a fair amount of experience using micrometers.

I would say that of the headspace nut is far off the zero mark, you've either got the incorrect model or something is far off about either your firearm or measuring method. Based on the instructions and the limits of typical headspace, your measurement should be within 10 markings on the nut of the zero mark (0.010").

Each full revolution of the nut is 0.050" based on the product pictures I see online. If the body stops at 1.5 and the nut is aligned at 5, the measurement would be 0.155".

Hope this helps.

thank you....

rugerjunkie · Nov 20, 2022

I think Hornady has a better tool for the task at hand.

CoalCrackerAl · Nov 20, 2022

I set mine how the casings fit in the chamber on bolt actions.

Head space and the RCBS Precision Micrometer

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