Ishapore 2A bolt question

[Peter Laidler]

Depends on what you call a 7.62mm field gauge. Bore or CHS? We (the UK Army.....) only use one(? there are a couple of exceptions) bore gauge for rifle barrels now. 7.62mm rifle. .297" gauge must run freely through the bore, without assistance and under its own weight. If there is any doubt about the bore, then range and accuracy test.

If it's the CHS field gauge you mean, then CHS limits for that rifle are one-offs. I forget what they are now but suffice it to say, what we call a 1.632 gauge might not equate to what the US call a 1.632 cauge due to the different way/place/diameter of the neck from which the calibration is taken.

In any case, don't even bother gauging it until you have proved that the bolt is the correct locking fit in the gun body

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[TCS-5]

Yes, I was refering to headspace gage.

I'm considering purchseing these two, 7.62 NATO GO (min) & NO GO (max) gages.
Headspace Gages (Gauges) - NATO Chamber

[Alan de Enfield]

This was written (in 2008) by an old armourer who seems to know a thing or two about the subject - think he still posts on here occasionally :

Now for the biggie, the 7.62’s. The basic principle of headspacing
hasn’t changed here but the practicalities have. Whereas before, on our
rimmed .303” rifles we measured the GO NO-GO distance between the
front face of the bolt and the rear face of the barrel, it’s all changed for
the rimless 7.62mm NATO caliber rifles. Now we have to measure
from the front face of the bolt to the cartridge seating at the neck. Well,
that’s all pretty clear then ….., except that the neck is tapered so where
EXACTLY on that neck do you take your GO, 1.628” and NO-GO
1.635 measurement from? Even if I told you it’d make no difference
whatsoever because without the specialist measuring and more
importantly, the calibration equipment, you’d still be none the wiser.
The trouble with this is that you’ve got to take the word of the
manufacturer of the gauge. And exactly where does HE take HIS measurement from but more importantly, WHO does he get them from.
geting difficult isn't it?
Let me give you an example. My GO gauge gives you a close/GO
reading of 1.628 but Bloggs & Co gauge may give you a GO reading
of 1.575” for the same 7.62mm caliber. How can there be a difference
of .053” between the two when they are identical? Well, it’s simple
really. Our STANAG gauges are measured from one diameter around
the neck while Bloggs & Co are taken from a different but larger
diameter .053” further to the rear! That is really all I want to say about
that.
The next obvious question for all you enthusiasts is where can I get a
set of these gauges and the true answer is that I don’t know!

The fact remains that
there are MANY gauges for all manner of 7.62mm rifles and machine
guns ranging from the little bolt action L8’s right through to the Lwhatever
it is ferocious mini gun. And there are equally MANY for
different lines of repair and functions, ranging from 1.622” to 1.648”.
a STANAG calibrated 1.6325 gauge (GO for the L1A1 rifle
incidental.....) then it will suffice as a NO GO gauge with your 7.62mm
Enfield provided that you slide a sliver of .003” steel shim across the
bolt face first, on the basis that 1.632 plus .003 equals 1.635.

On the other hand, if you’re clever, you COULD just have the rear face
ground down by .0045” to end up with a 1.628” GO gauge.
That just about covers the 7.62mm versions.

The question of
calibrating your gauges is one that needs to be looked into by ‘some
friends’ on both sides of the pond. I can see already that this is about to
open up a whole new can of worms...... But just hang on in
there....................