Ishapore 2A1 headspace gauge/ Measurement

[pcaru1]

I was wondering if I could determine if my 2A1 passses the 7.62 Nato max of 1.645 without buying the gauge. I did the fired shell with spent primer trick (You can see the length in the picture) but need to know how to measure for the headspace with this measurement on this rifle? I have a Forster field gauge of 1.638. Can I determine the headspace with these two lengths? Close bolt on field gauge and insert feeler gauge between rear lug and receiver? Or is this going to be too hard to determine?

This rifle is in near new shape with mirror bright bore and clean chamber. All matching except nose cap. It swallowed up a Forster field gauge, which I figured it would. Since I don't plan on putting thousands of rounds down range, I was hoping to save a buck without spending $30 for a one time use gauge. I don't want to assume it passes without checking.

Information

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[browningautorifle]

The primer sure backed out didn't it? Any way you can get the barrel turned in one revolution? Recut the chamber? I guess if there was then the gauge wouldn't be a problem would it?

[pcaru1]

The primer didn't back out, I took a fired round and de-primed it. Used to spent primer and started it in the pocket, chambered the round, and this is the result. Should be the size of the chamber to the bolt face. Unless I'm doing this wrong. Just need to know how to determine the right measurement.

[Parashooter]

Take an empty aluminum beverage can, cut a little ~1/2" disk from it, measure its thickness with a good micrometer, and stick it on the back end of your 1.638" gauge with a tiny dab of grease. Most common beer cans go about .004", which will give you a 1.642" gauge. Two layers will get you to 1.646" (or 1.647" if you lay on too much grease). If you need to measure closer than that, try a different beverage or spend a few bucks for a cheap feeler gauge you can cut up - or some precision shim stock (should you want to be real fussy).

[pcaru1]

I just did that exact thing and the bolt still closed on the gauge. I think I'm somewhere around 1.650 ?? Could it have been set up wrong?? If I'm reading it right, this has a #5 bolt head.
It looks like it has hardly ever been fired. Now what, wall hanger?

[Alan de Enfield]

You state the NATO max of 1.645 but Peter Laidler states 1.635 for Enfields in 7.62 So if its failing your 1.638 Gauge its 'had it' (although read the following)

Here are some notes from The Good Captain off the old Jouster Forum :

Anyone for 7.62mm CHS?
Posted By: Peter Laidler
Date: Tues 6 May 2008 11:36 am
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 L- whatever it is ferocious mini gun. And there are equally MANY for different lines of repair and functions, ranging from 1.622” to 1.648”.
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....................

[jmoore]

Captain Laidler's specs are for the L42a1s. What the Indian specifications were have yet to be disclosed, I think.

[Alan de Enfield]

Captain Laidler's specs are for the L42a1s. What the Indian specifications were have yet to be disclosed, I think.

Correct :
What I was trying to show was even if we know what the Indian headspace measurement is/are we have no idea what their datum point is, so, unless we had actual Indian calibrated gauges it is impossible to headspace.

A question for those more knowlegable than I :
Would it be safe to assume that using the same ammunition (7.62 Nato) in what SHOULD be a similar sized chamber (NATO Spec ?) that it would be safe to use L42 gauges and L42 headspace dimensions ?

[Thunderbox]

Measuring headspace on a 2A1 is a completely pointless exercise, if the manufacturer's specification is not known.

I doubt very much that 2A1s were ever intended to have the same headspace as a 7.62mm No4 target rifle - or a modern assault rifle - and that the no-go (if one actually exists) is probably well over 1.645.

[jmoore]

Would it be safe to assume that using the same ammunition (7.62 Nato) in what SHOULD be a similar sized chamber (NATO Spec ?) that it would be safe to use L42 gauges and L42 headspace dimensions ?

Not that that I'm more "knowed up", but I think Thunderbox's reply makes sense. As well, there are various headspace requirements even in the US for US weapons,- M14s run kinda sloppy, but match grade M14s and M21s are tighter, and some bolt guns are known to run tighter still. They will all still work fine with pretty much any old 7.62x51, dut it is a RELOADER's nightmare! Even chamber shapes vary a good deal between mfg's. Quite the bother.

Really, if the CHS it excessive, usually all that happens is case head separation (which prevents chambering the next round) or misfires (which is a bother). Not acceptable for a military weapon, but not generally dangerous in of itself.