A measurement can be obtained from measuring fired cases. PM Hungry.
Don't know about Cdn. sources for gauges, but Brownells or any of the reamer mfrs. in the US can supply gauges.
Besides using the proper headspace gauge is there any other method to do without it?
Also, where in Canada can I find the NATO headspace gauge not .308 win?
Get a "RCBS Precision Mic" from a2zoutdoors, its a head space gauge and a bullet seating gauge. Cartridge style headspace gauges are expensive, a pain to use (you either have to disass the bolt or mod the gauge) and don't tell you much with out purchasing a complete set (mucho expensive). Hungry or I can gauge your brass for you, PM him or me.