.50 cal Headspace Gauge

I have a .50 cal headspace gauge 2.217. 1966. Who is GGE ARMRS. USA made?
Why measure the headspace 2.217 from bolt face. How is it used?
Length is 60.5mm or 2.380".

Gauge%20a Gauge%20b

Whats with the crown marking (Swedish/Danish/Dutch?), could it be for a .50cal spotter application, maybe a sub cal trainer?.

Hi Ron,

This is a headspace gauge for a 12,7x76mm spotting-rifle M8. The gauge has the Nato-stock-number 5220-99-960-6547 (see the last 7 digits on the side of the gauge) and is called “Gauge, Armourers, Headspace”. The headspace for this weapon is 2.217, which is the distance between the boltface and the datum-line of the shoulder of the cartridge.
It has the code SM814, which is a number in the british systems, that is applied to
gauges, used in the British Army. Gauges used in the UK-military are normally marked with such a number and the crown, which explains the crown on the gauge.
The engraved letters “GGE ARMRS HDSPCE 2.217” means, in my opinion, “Gauge Armourers Headspace 2,217 inches”. At the moment, I can´t say if it is a go or no-go gauge due to the lack of the proper manual. Maybe one of the british members could answer this question.

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Thanks for this identification. It originally was covered in a rubbery/plastic casing but this cracked so I peeled it off.

Any info on the nationality of the gauge shown above?