Diagram of .308W & 7.62mm headspace gauge datums?

[Bruce_in_Oz]

Be careful with "NO_GO" gauges.

These often seem to be "weapon-specific", especially when you start working with machine-guns. I cannot remember offhand the exact figures, but the "official" NO_GO for 5.56 rifles (AUG, M-16A2 etc) are different and NOT the same as used on the Minimi LMG.

I know there was a difference between the NO_GO gauges for the L1A1 and the Parker-Hale M-82, and I understand that there is a different gauge again for the AI rifles. The NO_GO for the M-60 was different again.

SAAMI gauges are for "sporting" rifles and handguns. Belt-fed toys are a very different matter.

I will go for a dive in the crypt.