Space between chamber and breach block

[willyboy]

Originally Posted by Rick W.

The gap that you are mentioning, sometimes relates to folks two possiblities, headspace or case exposure(cartridge unsupported by chamber). It may or maynot indicate parts change out since original assembly, who knows, the numbers on the parts mean little anymore to those with basic concepts(shooting for instance) for the Luger in mind.

I find the comment on headspace a bit odd, as headspace is simply a measurement of the mechanism's ability to hold the cartridge in the boreline. One could think of a possibility of perfect headspace but half of the cartridge showing when the mechanism in in the locked position.

Case exposure on the other hand(some call this gapspace) is a relative term of how much of the sidewalls of the case are showing(unsupported by barrel proper), including the strengthened web(head) of said case. The Luger weak spots are the ejector slot and the feedramp(?) at the bottom of the barrel proper. As you know the Luger has a lot of parts that contribute to headspace and gapspace, one being the toggle mechanism's tolerance build ups.

There are numbers that people use for such parameters as headspace and gapspace. SAAMI here in the USA says some voluntary info on chambers and cartridge dimensions pertient to headspace. Europe and other parts of the world have their own words on such things.

You might peruse John's schematics or ask if there are numbers in those documents considering these two parameters.

Gunsmiths that I know pretty much adhere to the SAAMI for headspace considerations(wildcats excepted I reckon) but rely on their own experience for gapspace ideas/concepts. One would feel sure the Luger during its manufacture/design had those safety issues well in mind, but as you know, they controlled the manufacture/assembly/test all inclusively. Guns that are approaching 100 years of service, ............might have been touched some by collectors and shooters and others without regard to basic concepts of any type.

I have zero collector's interest, but somewhat of a poor man's shooter type. If the money is of any interest to you, you might keep this one in the drawer properly stored, rather than shoot it and let the collectors loose their interest in purchasing it later on with broken parts.

This is basically a foreign language to me. Could someone dumb this down for me?

[ithacaartist]

Originally Posted by willyboy

This is basically a foreign language to me. Could someone dumb this down for me?

I'll try. Rich is saying there are two measurements to take in this area. Headspace is the nominal dimension between the back end of the cartridge when it's seated properly in the chamber, and the face of the breech block that corresponds to it, the milled out area in its nose, thru which the firing pin protrudes.
Case exposure is how much of the brass case is visible?/unsupported by chamber structure. If you had an abnormally shallow chamber, the back end of the shell would hang out. You could still have a headspace within acceptable parameters if the overall length of the toggle train were short enough, by the amount the rim protrudes, but situations of excessive case exposure can be dangerous.
The pros have standardized data and measurements available to check against when making these measurements.