Originally Posted by JonM
All you really need for an ar15 is a field gage. To measure headspace on a ar15 you need to remove the ejector which protrudes through the bolt face the drop the field gage into the chamber if the bolt closes your barrel needs to be replaced. There is no removing the extension milling the chamber end down then reinstallijg the extension like you can do with other firearms.
Ar15 barrels are meant to be tossed and replaced once they exceed max headspacing.
so head spacing changes?! I thought it was set on manufacturing/assembly and it was good to go.
so, now one needs to check it over the life of the barrel? how many rounds does it typically take for the head space to open up?