As far as gauges are concerned, the Minimum gauge was .064", the Maximum was .074" and there was a Field at about .070". They look like the back part of a .303 shell except that they are made of steel.
Get a good micrometer ($20 at Princess Auto) and mike the rim thickness of the ammo you are using. If you have a DI cartridge case, resize it and use it: they all were .063" or so close that you could hardly measure any difference. Chop up a square inch of aluminum cooking foil into little squares. Insert the case under the extractor and slip in a couple of aluminum shims. Does the rifle close EASILY? If yes, try with 1 or 2 more shims, until you feel tiny bit of resistance as the bolt handle goes down. When you feel the tiny resistance, remove everything, throw away ONE aluminum shim and measure the thickness of the ones you ARE using. Add this to the thickness of your rim. This is your total headspace. You have the specs above. This is NOT the right way to do it, but it will work as a field expedient. I HAVE Army gauges and use them but I ALSO have 2 dozen .303s. I used this method, crude as it is, back when I had only a couple of rifles.
Why does your headpace need to be checked in the first place? If your rifle was safe when you got it, it will be safe now..... unless you have been feeding it a diet of straight PROOF loads, headspace changes only with thousands of rounds. If the bolt number matches the receiver number, or if you obtained th rifle from a reputable source, headspace should be okay. If you are not sure, tie the rifle to an old tire and fire 1 round with a string, then inspect the fired casing carefuly.
Headspace is so UNcritical with a .303 in general and with a Lee-Enfield in particular that I really question if most of the guys who jump up and scream "CHECK THE HEADSPACE!!!!!" actually understand what they are saying.... and that goes for the guy with 140,000 posts who now will flame me for saying this.
Headspace of the RIFLE is one thing, but you can have a RIFLE in perfect nick and still have excess headspace from lousy AMMO.... and it still will work perfectly.
Listen to guys like Tiriaq or Buffdog or Claven-2 or LouthePou. They KNOW what they are talking about.
On the other hand, if you really want to LEARN about your rifle, come on over to milsurps.com, take out a (free) membership and download a rifle manual AND the Armourers' Manual from the Military Knowledge Library, sticked at the top of the Lee-Enfield forum.
Hope this helps.
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