Metal God said:
Well, that cuts both ways, of course. I see "case headspace" and "cartridge headspace" as possible to misconstrue and you don't, except maybe by newbies. I offered examples authored neither by myself nor Mr. Guffey to say chamber headspace is what is meant in at least some instances. You offered anecdotal evidence from forum participation that indicates such misconstruing is unlikely. I think that sums it up. At this point, I suggest we just let it be a matter of personal preference what to use or avoid. There's no rule on the board that it has to be one way or the other.
I'll be interested to see if SAAMI ever does anything with it and if they do, whether they come up with a different term or decide to make Hornady's usage standard. I'm an ASTM member and our standards are created the same way. Any member can propose a standard to the appropriate committee at the annual hotel conference room gatherings and the committee can decide to ballot it.
Re the gunsmiths, cutting a chamber to size is usually called "setting" or "establishing" headspace. "Headspacing on" usually introduces what cartridge surface stops against the chamber. In the chamber, that stopping surface is called the cartridge seat, so you could say "cartridge seating on" instead of "headspacing on". The only time I've heard of a chamber being "headspaced" was either in the past tense (as in "was the chamber headspaced correctly?"), or in describing setting up headspace in the variable Savage actions.
There's always been at least some variety in the descriptions because what you measure for headspace in rimless bottleneck cases has changed post-SAAMI being organized. If you look up the headspace of a .30-06 chamber in Hatcher, it is measured from the breech face to the shoulder/body intercept. Indeed, the 30-06 and other old rimless cartridges use that and have a slightly wider shoulder angle on the case than is used in the chamber, forcing the corresponding outside corner of the cartridge case shoulder to seat on the chamber rather than the slope of the shoulder. It's not easy to measure a chamber's body/shoulder intercept accurately.
SAAMI came up with the shoulder datum idea in the '30s or '40s, I think, precisely to make the measuring easier. I don't believe the military adopted it, as the blueprints I've seen don't have a datum dimension on the chamber shoulder, but the military certainly did come up with headspace GO, NO-GO and FIELD REJECT gauges. The European CIP doesn't use a datum. The datum is really only reaching its potential value when the chamber and case shoulders have the same angle, as modern designs use. The old cartridges thus have two different measurements of chamber headspace possible, owing to the gap at the shoulder surfaces left by the difference in shoulder angles. One for the cartridge and a slightly longer one for the chamber when the case clearances are zero.
Here's an interesting aside: from Forster's description, it appears their Bushing Bump die would eliminate the .30-06 (and .270 Win, for example) shoulder angle disagreement with the chamber if they make the top end of their die match a minimum chamber rather than a case shoulder angle. Upon bumping into the shoulder, it would set the old cartridge's case shoulders to match the chamber better.
. Hmmm how could we go so long without a fight and closer ? I wonder what was so different about this thread then all the other closed ones ? 