Will a .308 field headspace gauge tell me anything useful in a 7.62x51 Enfield?

[1KPerDay]

I have an Ishapore .308 enfield that may have excessive headspace... will a .308 "field" gauge be of any use? I know the go/no-go/field specs are slightly different between the two cartridges but I haven't had luck finding a 'field' gauge in 7.62. Nor do I know whether Ishapores have different specs than US 7.62s, for which all of the gauges I've seen have been made.

Any input welcome.

 

[bigedp51]

Every country has different headspace standards for the 7.62 NATO and no one knows what the headspace settings are for the 7.62 Ishapore. Example, the British L42 7.62 NATO Enfield sniper rifle has headspace settings tighter than American SAAMI .308 headspace.

On the No.1 Enfield .303 you can have as much as .016 head clearance or air space between the bolt face and rear of the case with American made ammunition.

My 7.62 2A1 Enfield had .012 head clearance which can be measured with a set of feeler gauges.

Below is a No.4 action showing where to place the feeler gauges to check head clearance. Place a empty unfired cartridge case in the chamber, to get a better reading it helps to dissemble the bolt but if you push forward hard on the bolt you can still get a good reading.








Below is my 2A1 Ishapore and remember this, the No.1 .303 bolt heads are rated for lower pressures than the 7.62 NATO and you will "NOT" find any Indian Ishapore made bolt heads rated for higher .308/7.62 pressures. Let me know what your head clearance is checking with a feeler gauge. There is a second way to measure head clearance/headspace on the Enfield rifle without headspace gauges.

 

[triggerman770]

7.62x51 nfield

here is a comparason of the 308 vs 7.62x51 guages. If you were to use a field and it closes you can add pieces of tape 1 layer at the time(each layer is approx 001") to determine how much headspace you have.
Then you could look at the 7.62x51 cart dimensions to determine if it is safe or not. If the total headspace in the rifle exceeds the GI no go specs you will most certainly get incipient case separation usually within .250 of the casehead. Those old bolts just won't take 51Kpsi comming at 'em:what
308 Winchester (SAAMI) Headspace 7.62 NATO (Military) Headspace
GO - 1.6300" GO - 1.6350"
NOGO - 1.6340" NOGO - 1.6405"
FIELD - 1.6380" FIELD - 1.6455"
Also remember the nato case is thicker and will withstand more pressure than a commercial case

 

[1KPerDay]

Thanks guys! Big Ed, when you say "it helps to disassemble the bolt" what do you mean exactly? Just remove the extractor? What's the purpose of the unfired case in the chamber?

Does measuring bolt head clearance truly give you any idea of headspace?

 

[bigedp51]

What actually causes the problem isn't headspace, what causes case head separations is "head clearance". When using a feeler gauge on the Enfield action you are gauging the head clearance or "air space" between the bolt face and the rear of the cartridge case. (thats why you need a new or resized cartridge case)



When you push the Enfield bolt forward what you see between the receiver and right locking lug is "head clearance".



The thickness of the feeler gauge is head clearance and a cartridge case is required to be in the chamber. (a resized or new case, a fired case will be longer and give a false reading)



Now go look at your Ishapore chamber, it is smoother and chrome plated and designed to prevent case head separations due to its lower friction. These 7.62 NATO Enfield rifles were designed by the Australians who at one time planed to produce these same Enfield rifles.

These 7.62 No.1 Enfield rifles were designed with longer headspace because the cartridge is the "sacrificial" component and lowers bolt thrust.

 

[1KPerDay]

Thanks again...
2 questions:
1. will the measurement work the same even though the 7.62 doesn't have a rim like the .303 in your illustration?
2. How does one know if the forward movement of the bolt (when pushing it forward) is being stopped by the cartridge case in the chamber, rather than the bolt head or other parts of the bolt contacting the rear of the barrel or lugs or something? Perhaps I don't fully understand how the enfield bolt locks up.


Also please confirm whether I need to remove the extractor for this test or not.

 

[bigedp51]

The bolt does not require to be dissembled to check headspace, BUT if the measurement is close the bolt was required to be dissembled. This includes the extractor, cocking piece, firing pin etc. just the bolt body and bolt head were used.

With the bolt completely disassembled the measurement is far easier to check.

The rimed .303 cartridge case does not mean anything as far as headspace goes, the only difference between a rimmed, belted or bottle neck case is the distance from the bolt face to the datum line.




Please note, I have headspace gauges for both the .303 and .308/7.62 Enfield rifles. What I'm trying to get across to you is you do not need headspace gauges to check an Enfield rifle.

Second method for checking headspace/head clearance using a set of Vernier calipers. And the bolt does not need to be dissembled.

Measure the overall length of your unfired or resized cartridge case and write it down.

Next seat a fired spent primer in your test cartridge case using just your fingers. Your going to seat the primer with the bolt face and the amount it protrudes after chambering is your head clearance or air space.







Now chamber the test round and slowly close the bolt and then remove from rifle. Now remeasure the overall length again and write it down.

Now subtract the first case length from the second case length and this measurement will be head clearance or the "air space" between the bolt face and rear of the case.

Now the last batch of new unfired .308 cartridge cases were -.002 to -.009 shorter than minimum headspace or the GO gauge. At maximum headspace you can have as much as .017 head clearance on the enfield rifle.

My Ishapore 2A1 had .012 head clearance and I could fire both .308 or military 7.62 ammunition without any problems. "BUT" the commercial cases went in the trash and were not reloaded because of stretching in the web area. (as did my .303 cases if not fire formed correctly)

Just remember this, the Enfield rifle is not made to American SAAMI chamber and headspace standards and it is also not made to U.S. military M14 headspace and chamber standards. And NO ONE knows what the headspaces settings are for the Ishapore 2A1 7.62 rifle. And NO ONE has bolt heads proofed and tested for the higher 7.62 chamber pressures.

 

[1KPerDay]

Thanks again. I was aware of how the headspace was measured differently between rimmed and non-rimmed cartridges, but I was just wondering if that would have an influence on the method of using feeler gauges to measure bolt head clearance. Since the rimless case needs to be pressed up against the shoulder in order to contact (or not) the bolt face, whereas the rimmed cartridge is, I assume, a known thickness and logically (to my mind, anyway) would seem to allow for a more consistent measurement of "open space". I suppose it effectively amounts to the same thing.

Thanks again for your patience.

 

[bigedp51]

1KPerDay

My screen name is bigedp51 but my real name is Ed Horton and 95% of all Enfield books and manuals you see today on the internet were collected, scanned and converted to Adobe format for free download by yours truly.

Below are just a few.

 

[1KPerDay]

Cool.

 

[Jim K]

Hi, 1KPerDay,

The above is good info, but what makes you think your rifle has excess headspace? Are you getting stretched or separated cases? Other problems?

Jim

 

[1KPerDay]

http://www.thehighroad.org/showthread.php?t=595460

There are differing opinions on the cause (bad headspace, bad ammo, or some combination of both) but I want to confirm safe headspace before firing it again.

 

[bigedp51]

1KPerDay

Lay feeler gauges next to your fired primers and tell us approximately how far the primers are protruding from the rear of the case.

2nd, steel cartridge cases are not as elastic as brass and as far as I'm concerned I would never shoot them.

3rd, if you have over .017 head clearance you can start worrying about headspace.

4th, the bolt head can be replaced with a bolt head marked with the letter (S) for spare which are longer than normal. BUT the No.1 303 bolt head was used for a cartridge producing 45,000 cup or 49,000 psi or less chamber pressure than the .308/7.62. This has been done BUT besides the pressure difference "fitting" the bolt head properly isn't something you do by just getting one new bolt head because it might over rotate and not be a tight fit.

5th, I sold my 2A1 and bought a Stevens 200 with tighter headspace that didn't ruin my brass cases for reloading.

6th, you can send your Ishapore 2A1 to Brian Dick below and he will fit a new bolt head to your Enfield rifle.

http://www.bdlltd.com/BDL_LTD/About_Us.html

And remember your Enfield rifle was designed to shoot military ammunition made to withstand longer military headspace settings. And your 2A1 was never designed to shoot steel cased ammunition.


If you think you have a headspace problem then look at the photos below and remember military cartridge cases have much thicker base web areas than commercial cases do. Also look at the center cartridge in the photo and see how far the primer backed out and is protruding.

 

[1KPerDay]

I will heed your (and others') advice and will not shoot steel ammo in this rifle again. Do you think it would be useful to fire some some nato brass ammo through it and perform the checks you recommend? I assume your nifty primer seating check is best performed with brass ammo anyway.

 

[bigedp51]

The Winchester ammo below was the first ammo I fired in my 2A1 because the pressures were lower than military. Remember there is "rated" chamber pressure and what pressure the factory actually loads the cartridges to which is lower than military pressure loadings. I also shot these first to see how much they would stretch compared to military cases.



After firing five rounds I checked the cases for thinning and stretching in the web area of the case. These commercial/semi-military cases stretched and thinned .010 so I just tossed them in the trash rather than reloading them and having them fail the second or third time they were reloaded.



There is far less chance of having a case head separation with military 7.62 ammunition at the longer headspace settings. But until we see your head clearance figures we are in the dark as to your Enfield.

 

[1KPerDay]

Not sure if I'm doing it exactly the way you want, but with nothing in the chamber and the extractor removed, the .020" feeler will go if I press forward on the bolt, and with a Lithuanian 7.62 Nato case in the chamber the .005" feeler will go but the .006" won't.

That's good, right?

I also looked at the bolt head to make sure it wasn't over-rotating when screwed all the way in, and it isn't.

I still can't get the bolt closed with the extractor in place and NO case in the chamber (the nose of the extractor is hitting the ramp rather than 'ramping' up and springing outward. If I chamber a dummy round from the magazine the bolt closes fine.

Let me know if this provides you with any useful info.
thanks again

 

[bigedp51]

1KPerDay

Your headspace is fine if you only have .005 head clearance.

If your bolt will not close you have the wrong extractor installed or the extractor is installed incorrectly.

As the bolt closes the extractor should move away from the case to the right into the extractor cut out in the barrel. You might have a No.4 extractor installed in your No.1 Enfield.

 

[Jeff F]

1KPerDay I think if you shoot brass cased 7.62 all will be good. My friends shoot 7.62 and factory .308 with no issues. A couple of them reload for their 2A's and they just bump the shoulder back a touch and neck size just like we do for the .303 and they get fairly good brass life. Enjoy your Enfield.

 

[1KPerDay]

1KPerDay

Your headspace is fine if you only have .005 head clearance.

If your bolt will not close you have the wrong extractor installed or the extractor is installed incorrectly.

As the bolt closes the extractor should move away from the case to the right into the extractor cut out in the barrel. You might have a No.4 extractor installed in your No.1 Enfield.

As noted in the other thread, the rifle functioned perfectly until I had that case failure. After that the bolt will not close on an empty chamber with the extractor installed. I can't for the life of me see any damage at all to the extractor. I did not remove the extractor until it stopped closing, so I can't see how it could be installed incorrectly. It is the extractor that came on the rifle and it worked for a few dozen rounds (all I've shot through it) before the case failure.

There is a small indentation in the extractor groove/ramp in the barrel where I ASSUME the nose of the extractor is hitting when a case isn't present. I can't see any damage to the bolt head or extractor.

The fact that it was working before and isn't now to me would seem to indicate that something was bent/damaged/affected by the case failure, but I can't determine what that something would be... unless there was some grease/crud in the space between the front of the extractor and the bolt head that was blown out by the gas, and that now allows the tip of the extractor to move further toward the bolt head than it should (and that it was like this the whole time but the cosmoline/crud/whatever was helping it function properly before). That's my best guess.

 

[Jim K]

There is something very odd about that ammo. Even with way excess headspace, there is no way a case should blow out in the extractor groove; that should be the most solid part of the case. (BTW, is Herters back in business? I haven't heard of them for 30 years. Or is the ammo that old?)

As to the rifle, have you checked the lug seats in the receiver. Under high pressure, a bolt can set back hard enough to compress the lug seats (create a "dent") so that if the bolt is tight (as when a case is seated) the lugs are in a depression and can't turn.

If that is the case, it means, of course, that if the rifle did not have headspace problems before firing that ammo, it does now. I have no way of analyzing that ammo or the rifle at long distance, but I think I would discuss the problem with Cabelas about the source of that ammo and possible damage to the rifle. If they refuse to cooperate, the only recouse would be legal action. Trouble with that is that an hour with a lawyer would cost twice what a new rifle would.

Jim

 

[Jeff F]

Get a dental pick and scratch around in the extractor groove. That blown steel case could of blown some hot slag up in there.

 

[Jeff F]

Jim, Herters is reboxed Wolf ammo sold by Cabelas.

 

[1KPerDay]

As to the rifle, have you checked the lug seats in the receiver. Under high pressure, a bolt can set back hard enough to compress the lug seats (create a "dent") so that if the bolt is tight (as when a case is seated) the lugs are in a depression and can't turn.

If that were true, wouldn't it refuse to seat even with the extractor removed? Or with a case in place? As noted, when chambering from the magazine and/or with the extractor removed, the bolt closes perfectly. IMO the issue is the extractor/extractor ramp. What's still confusing me is why it was working before.

I agree the ammo is questionable... and if BigEd's opinion of my headspace is accurate (that it is not excessive) we can rule out that as a contributing factor in the ammo's failure. I will perform the primer seating test also and see what that says.

 

[Jim K]

I think I am getting confused here with all the comments. Let me see if I understand.

With ammunition, the rifle feeds OK from the magazine and the bolt closes normally. But with no ammunition, the bolt won't fully close. Is that correct? If so, it seems that the extractor angle is not riding up that little ramp, just as you say. With a round under the extractor, the extractor is pushed far enough outward that the extractor goes in OK.

Studying those cases, I think it is possible that escaping gas could have impacted the front of the extractor, bending it down just enough to change the way it contacts that little ramp. (A gas impact on the part that grips the case will bend the extractor at the thin part and move the tip of the extractor inward. To visualize this, hold your arm up and your hand with the fingers bent at a right angle to the palm, then push the fingers down towards your arm; the wrist will bend, and the knuckles will move toward the fingers.)

First, check to see that the extractor still grips the case properly and that the rim fits under the extractor OK. I wouldn't try to bend the extractor back. If you can't find a new extractor, try some CAREFUL work on the nose of the extractor with a Dremel tool, moving the angle out so the nose of the extractor won't hit the edge of the barrel head on. Don't touch the inside part of the extractor that grips the case.

Jim

 

[1KPerDay]

I think I am getting confused here with all the comments. Let me see if I understand.

With ammunition, the rifle feeds OK from the magazine and the bolt closes normally. But with no ammunition, the bolt won't fully close. Is that correct? If so, it seems that the extractor angle is not riding up that little ramp, just as you say. With a round under the extractor, the extractor is pushed far enough outward that the extractor goes in OK.

Correct.

Upon rereading the other thread one gentleman suggested that perhaps the "dent" or divot in the extractor ramp was caused by expanding gas, and it may help to polish that out (see the pics in that other thread). I'll try to do that first and then try your suggestions. Thanks