Description
Original WW2 British Issue Armorer’s Gauge
Gauge No. 3972
Unlike the other pattern. The markings were done by hand by the Music company in the UK
This is designed to measure the protrusion of the firing pin on the Thompson SMG.
This is critical since the Thompson bolt headspaces from a surface inside the receiver rather than the back of the barrel like most SMGs, so the firing pin protrusion when the hammer is depressed by that inside receiver surface would be critical.
