Where in America can I buy

[72 usmc]

Not sure what they still have, I thought most are long gone. A British military, original headspace gauge "Go" would be size 0.064. Like Alan indicates the originals were called GO (.064) and NO GO (.074). The Apex web page is kind of difficult to work with. It is neat the different shapes and to have an original for display.

SB, I just found this Go at .064 original. Too bad it's not a NO GO at .074

https://www.brpguns.com/sm-139-armorers ... r-303-064/