I would have to look at the setup you have, more, but you'll most likely have to take a dimension from a shoulder on the barrel to its breech end, to see how much goes inside the receiver, then a measurement where it abuts the frame to the face of the bolt when closed, to calculate it.
There will generally not be very much clearance at all from the bolt face, or edge of the bolt when its face is recessed, to the breech end of the barrel. Just enough for the bolt to freely turn so there's a minimum gap between the two. In a recessed bolt face, like on the 700 Remingtons, the cartridge sticks out of the end of the barrel, and into the recess to where the extractor can go into the extractor groove. If I recall, there's not very much of a gap between the two, and only the solid brass surrounding the primer sticking out of the barrel, with all of the cartridges tubular portion in the chamber. Really, the stick out should be just enough for the extractor to reach the groove when closed. If any of the wall of the cartridge is exposed, its the same as too much headspace, and would rupture.