Re: .50 BMG Shooters
The bolt nose recess dimension won't tell you much. The distance the cartridge sticks out of the barrel or chamber is dependent on the action used. Some sit in a recess so the cartridge is near flush. Head space is still measured with gauges and a depth gauge. With a cone nose bolt you measure from the shoulder of the barrel to the bolt face and compare the shoulder to Go-Gauge to determine headspace.
What are you working on?
Build a man a fire and you heat him for a day.
Set him on fire and you heat him for life.
Only accurate rifles are interesting.
Gordy and Brady.