Hi Alan, I'm not sure if this will post again but here goes.

I've been reading these posts on 308/7.62 and head space and am now not only baffled but worried...
I fully get the business about pressures and different measuring standards, not to mention thicker cases and the whole biz. No worries, I'm not reloading, no problem there, but I'm baffled as to head space.

What's concerning is that as you've pointed out the different gauges bear on the chamber in slightly different places and that in turn means that measurements taken at the cartridge base might be correct safety wise but will probably be different number wise for each gauge if measuring the length of the firing chamber to the cartridge base.

eg if I get my 7.62 ishapore, and use a no go for 308 winchester in it, is it possible that it might say all is OK, but when I use a 7.62 no go gauge it might say all is no go...and all that comes about as a result of the no go gauge being slightly further in or out depending on its design.

I know this because at the moment my rifle is too tight, so its very easy to see the differences.
When I strip the extractor off and firing pin out, and test the bolt and head with a 7.62 round in the chamber, then a 308 winchester round, and then one of those safety fire fake cartridges (?name) the bolt tightens up in three distinctly different spots, roughly about 15 degrees apart.
If I resurface the bolt face so that its correct with the .308, will it now be too loose for 7.62?

One measurement would reassure me if someone knows it; with a 7.62 round chambered, what is the acceptable maximum and minimum gap between the cartridge base and bolt head face?

Ok, now that would be great if I'm shooting nato rounds.

If I'm using 308 winchester, what is the acceptable max and min gap allowable between the cartridge base and the bolt head face?

Quote from Peter above;
As for 7.62mm CHS gauges, in Britainicon, we had MANY variables. BUT, so far as this forum is concerned, we only had ONE set for bolt action rifles..., from the L8 series, right up to the L81 and that is 1.628 GO and 1.635 NO-GO.

Can I interpret that to mean a maximum gap of 7 thou, ie the difference, for 7.62 rifles?

sorry if we've covered this, but its giving me a headache trying to decide exactly how to make my too tight rifle safe to shoot. thanks to all...