11 Nov 2010
Don't know what you mean about internet myth regarding SAAMI. Since most ammunition and cartridge cases encountered these days are SAAMI spec vs military, SAMMI headspace gauges are what one should use. SAAMI gauge may indicate a fiream unsafe to fire and unless using military brass with thicker web I'll go with the SAAMI gauge's indication every time even if it passes military tolerances.
SAAMI .303 "no go" is .067". The correct design headspace gauge to use is the Commonwealth "Field" of .074" (war use tolerance allowed up to 0.84"). Not surprising that some perfectly in-spec rifles "fail" a SAAMI gauge, as the correct minimum "go" is 0.64".
Thus SAAMI spec was wrong from the outset, and now some US manufacturers make cases with thin rims that would not pass a standard military quality check if that ammo were being procured today.
In Europe and most of the world, shoooters are best to ignore SAAMI and stick with the real headspace specs, as all surplus and most modern and recent production (HXP, PMP, Privi, Wolf, S&B, PPU, Kynoch, etc) use the normal military dimensions.
In US you have the silly situation that two specs of ammo are in circulation, but the majority of shooters don't understand the situation. This has spawned a vast internet headspace confusion, and a scramble for longer boltheads to "tighten up" headspace. The ironic thing is that most of these "headspace tighten-ers" are probably actually (a) making an in-spec rifle out of spec (most have no idea about fitting a bolthead correctly); (b) actually accelerating wear on their rifle by then having over-tight headspace when they come to use military-spec ammunition.
The other factor in this is that over-generous head space has no real effect other than possibly to shorten the life of poor quality (thin) brass. Ergo, its best to stick with the specification that was designed into the weapons system.
source: https://www.arrse.co.uk/community/threa ... st-3493020
British specifications NO GO .074, GO .064 military
SAAMI USA specifications Clymer gauges are Go .064, NO GO .067, FIELD .074
Mosin 7.62x54R coin gauge specifications military
GO .065, NO GO .073, FIELD .076
The FireWerks gauges for 7.62x54R measure:
"Go" measures 0.0655", 1.66mm "No-Go" measures 0.0725", 1.84 mm "Field" measures 0.0755", 1.91 mm
The Forster gauges for Enfield .303 British measure (from published data):
"Go" measures 0.064", 1.62mm "No-Go" measures 0.067", 1.71 mm "Field" measures 0.070", 1.78 mm
Those Forster gauges for .303 are to the SAMMI spec. British Field allows .074 inch.
The Okie coin gauges and Yankee military spec coin gauges measure :
GO = 0.064" NO-GO = 0.067" FIELD = 0.074".
Both Forster and Clymer bullet style gauges are made to SAAMI
specifications not military specs. Use a Forster or Clymer bullet style headspace FIELD gauge on an Enfield and it closes on it, the rifle could still pass on a military spec .074 gauge. I like Military specification gauges for my surplus rifles.
Hence, if you need a cheep coin gauge for an Enfield that is available in the US only, Firewerks makes Mosin gauges and you should buy a Mosin NO GO that should measure .073. This gauge can then be utilized as an Enfield FIELD .074 gauge. Since for the last 25 years I have the wrong gauge for my Mosins, I ordered a Mosin Firewerks Field gauge and it should measure .0765 not .074 like my Yankee FIELD coin gage does. I must have been sent the wrong gauge although it has 3 lines indicating a FIELD gauge
We shall see.
I will report its thickness measurement after I receive the Firewerks FIELD MOSIN gauge and confirm its actual size.
They also sell a 3 set and a 2 set with the field and no go at $40. In my crazy world, if war time specs go up to .084 allowing .020 headspace. Heck, I would be OK checking Enfields with the Mosin larger Field gauge of .0765. If they fail on that Field gauge, I'd leave it on the table.
To old to fight and to old to run, a Jar head will just shoot and be done with you.