All this headspace information

[Alan de Enfield]

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! But here’s what I propose. If you HAVE a set of spurious/said to be/reported to be/hope they are 7.62mm headspace gauges, I will calibrate them for you and tell you EXACTLY what it is you have. 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”.
Once I return them, calibrated, at least YOU know that if the ‘unknown’ gauge you sent to me to be calibrated comes back as 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....................

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[ireload2]

As for 7.62mm CHS gauges, in Britain, we had MANY variables. BUT, so far as this forum is concerned, we only had ONE set for bolt action rifles..., from the L8 series, right up to the L81 and that is 1.628 GO and 1.635 NO-GO. The other sizes relate to machine guns where heat, expansion and locking/unlocking methods all come into play.

On the basis that these figures are correct for British made bolt action 7.62mm rifles, then I see no reason why these figures should not be absolutely correct for Indian made Enfield Rifles.

The problem is anyone can make a 7.62mm gauge and call it, well, whatever they like! Ours are all calibrated from a diameter around the neck to the base. I can check the calibration of your SAAMI gauges against ours

If you are that concerned about accuracy of a gauge you should never "calibrate" one head space gauge vs another. Rather the gauge should be check with the appropriate measuring equipment accurate to 10% of the required tolerance specified on the gauge drawing.

[Jim K]

I used to try discussing the headspace issue here but gave up in the face of total ignorance from those who had not the foggiest idea about what headspace is or how it can affect anything.

I read that rimmed cartridges can't have excess headspace, that Lee-Enfields are immune from headspace problems which apply only to those nasty Mausers, that any and all headspace problems can be eliminated by neck sizing cases, that L-E chambers are deeper so headspace is not an issue, etc., etc. All blithering nonsense, but it seems to be what the L-E crowd believes, and nothing will change that.

By the way, a headspace check on a used rifle requires only one gauge, a Field Reject gauge. GO and NO GO gauges are not needed, nor are shims, pieces of cardboard, feeler gauges, bats' wings, and magic incantations.

Jim

[jmoore]

Good grief!

[Peter Laidler]

But I DO have the calibration gear................................ But OUR gauges don't equate to some of YOUR gauges and YOUR Enfields are gauged to OUR inspection standards

[IditarodJoe]

According to the folks at Clymer, either .303 British or .30-40 Krag gauges will work to check your No. 4. They're interchangable.

[Peter Laidler]

We're getting into VERY muddy water here.............

If you got a Ford car, fit Ford parts is what I say. But maybe that's because I'm very inexperienced with these things....................

[Amatikulu]

Gentlemen,

This thread contains a number of unnecessary personal jabs. Please refrain from such behavior - I don't need any extra work at this time.

[villiers]

Personally, I´d never trust myself to do any work on a rifle that might effect its safety or integrity (quite apart from it being illegal here in Germany). So I had my .308 conversion LE No. 5 checked by an authorised gunsmith and proofed. That´s what they´re there for.

[John Sukey (Deceased)]

It would be nice if Clymer provided headspace gages to BRITISH MILITARY SPECS instead of SAMMI specs.

What are the odds that you would find a .303 rifle set up to SAMMI specifications rather than British? How many current sporting rifles are made in .303???????

As far as I am concerned, SAMMI gages are a waste of time in .303 and the person who was thinking 30-40 Krag rim thickness is the same as British .303
must have been smoking funny cigarettes!