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Win barrel on S'G'?
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Dan Pinto, Photo Editor

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I believe the hole on the bottom to be a gas hole.

the gauge to check the bolt measures from the back of the lug to the seat face (where the bullet rests)
it also measures the lead or front of the lugs.

There are a few ways to improvise the measurements to compare on to another. This would require more than most people have access to.




Edited by New2brass - Aug 17 2020 at 8:49pm
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Based on a drawing I have, to be in-spec. a USGI bolt cannot be longer than .560 or shorter than .558 measured from the rear of the right bolt lug to the bolt face. Assuming this spec is correct and the bolts were manufactured to spec, .002 is all you can ever hope to gain and you would need to have a short bolt you are replacing with a long bolt to realize any head space improvement. 

Of course, that is the math on paper. Mileage may vary in the real world.
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Originally posted by New2brass New2brass wrote:

I believe the hole on the bottom to be a gas hole.

the gauge to check the bolt measures from the back of the lug to the seat face (where the bullet rests)
it also measures the lead or front of the lugs.

There are a few ways to improvise the measurements to compare on to another. This would require more than most people have access to.



The hole is a "drain" or to assist in cleaning out the ejector bore;
look in a "clean" bolt and you can see the ejector spring.
Don
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Don, I stand corrected!
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Thanks floyd.
I will add some tape to the gauge and measure. I have a nice caliper to use. 
Regarding the 9mm bolt, I am a little confused with what 'face opened up' entails? Is that something a gunsmith would do? Or at home with a dremel LOL?
Best regards
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Originally posted by colreed colreed wrote:

Thanks floyd.
I will add some tape to the gauge and measure. I have a nice caliper to use. 
Regarding the 9mm bolt, I am a little confused with what 'face opened up' entails? Is that something a gunsmith would do? Or at home with a dremel LOL?
Best regards

You will not have to touch the 9mm bolt other than loading it with spec. USGI guts, they all fit. The only difference between the two is the skirt around the bolt face has been milled a bit for it to capture a 9mm base, which is about .010 wider in diameter than the 7.62x33. The IJ bolt is longer than any GI bolt I have found. It’s just the way IJ manufactured them.

I certainly do not advocate the long-term use of a cast bolt. They are inferior to GI forged bolts. The thing is that if you measure your head space and determine it to be out of spec by some .003-.004, or less an IJ bolt will pull it back in.

I suggest this because the other option is to hunt for a GI bolt that might work, or go for the barrel change to correct it if desired. IJ 9mm bolts are available in the $110 range. The GI bolt prices have generally increased, like most other carbine parts.

If you can stand the thought of having the cast IJ bolt in the gun, it can improve head space by .003-.004. If you are out past 1.305-1.306 when you shim your gauge and determine actual head space....may as well plan for a barrel replacement if you desire the head space to be in spec. 

Let me be clear. The only reason I suggest the 9mm bolt is that they are available. The 30-caliber IJ bolt would also work, but I have been searching for one for quite a while with no success in finding one.
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Roger,
Thanks for all that. Without knowing my actual headspace, I am sort of fumbling around in the dark. I  will get a measurement, hopefully today, and let you know. You have, however, already laid out all available options in quite well detail, so I should be able to make an informed decision once I have the measurement. I appreciate it. 
Best regards
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Roger,
I just finished adding layers of scotch tape to the base of my field gauge and this is what I got:

gauge with no tape = 1.300  Closed easily
gauge with 1 layer  = 1.302  Closed easily
gauge with 2 layers = 1.304 Closed easily
gauge with 3 layers = 1.036 Closed easily
gauge with 4 layers = 1.038 field gauge did not close

I repeated the procedure several times just to verify.

Also, I did find a post war round U bolt on another of my carbines, and I tried it out. Exact same results. 

I believe it is time for me to give up on this barrel as has been suggested. And again, many thanks for your inputs.

Best regards
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I think I am correct to assume the last two measurements have the 0 and 3 transposed?

Yes sir...looks like it’s pretty far out and no bolt is going to tighten it up enough to head space with your 1.300 gauge. 

I do not insinuate doing anything at all dangerous, but as long as the extractor will snap-over a rim and the firing pin will ignite the primer, it will shoot. 1.308 is getting a bit sloppy though. In my experience, 1.310 is about as far as you can go and still expect it to shoot firing average-length brass.
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OOPS! Sorry 'bout that. Yes, the numbers are transposed in error. My bad. I should learn to proof my scribble better. 
I suspect the previous owner might have been unaware,.....but perhaps maybe not since the Win barrel is unusual for the S'G' receiver. Who knows. Could it have been installed during rebuild? Certainly not in its current condition. Armorer would have rejected it. Since the muzzle measures just at 1.0, it doesn't appear to have seen a lot of use. 
It is curious to think about all the possibilities. But, have to move on. Quite some time ago, someone referred to 'shot out' barrels as good tomato stakes. LOL. Guess I'll stick it back for some later possible use.
Again, many thanks for your expertise, time and concern. 
Best regards
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A barrel with that much life left in it, one would have to think it was installed and improperly head spaced. There are many, many shot-out barrels out there in carbines that head space well. It seems to me that it takes a lot of abuse to wear-out a chamber b4 a bore. Smells like it was installed that way, or maybe on some other receiver and wound up on that one. People that don’t know any better or don’t care just shoot ‘em and never consider what the head space is. Also, maybe people that do know and do care realize the gun will continue to shoot....and just shoot it.

A good comparison might be 9mm. SAAMI allows similar head space tolerance and about any 9mm semi-auto presents a certain amount of unsupported brass beneath the chamber, which the carbine doesn’t. 9mm is rated very similar in pressures as well. You never hear about head space concerns from 9mm semi-auto shooters. People just shoot ‘em and they will shoot until the brass gets too short.
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As usual, good points to ponder. You take care Roger. Best regards.
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I'm going to ask what hasn't been asked...What if it is the receiver that is bad and not the barrel. Same result, but different cause. I think you need to check to see if the receiver is still in spec.
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Strangely, I had a similar thought. What if some extra material, just a few thousands, was added to the front face of the slot where the bolt rotates to the closed position? This would permit the bolt to close closer to the loaded casing. 
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The right skilled craftsman could likely do that, but the cost to do it might be more than grabbing another barrel and you will have a forever welded receiver. 

There is a member here on the forum that said he planned to make an attempt to do that very thing, or beef-up the rear bolt lugs. Have not heard if he succeeded. I believe it was a commercial.
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It would be easier to add material to the bolt face. Tin it with a high copper silver solder. It will wear okay. Maybe you might have to dress the extractor a little if it's too tight. I don't think there's anything wrong with the receiver. The chamber was just reamed too far. Can't fix that.
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Originally posted by jackp1028 jackp1028 wrote:

It would be easier to add material to the bolt face. Tin it with a high copper silver solder. It will wear okay. Maybe you might have to dress the extractor a little if it's too tight. I don't think there's anything wrong with the receiver. The chamber was just reamed too far. Can't fix that.

I thought about that myself Jack. I’d rather ruin a bolt than a receiver. Firing pin may have to be altered...maybe? There is probably a limit and this one is out by at least .005-.006, based on a 1.300 gauge.

I doubt there is anything wrong with the receiver as well. I have also heard of another fix, but again it requires the right guy with the right tools. Machine the breech and install a sleeve that can be reamed? Far out maybe, but it would save another otherwise good GI barrel.
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Welding on the receiver is not a good idea; if it does not warp, it will be soft and need "re-hardening".
I don't know of anyone who would undertake to treat a finished receiver.

I subscribe to the "just reamed" too far explanation.

It is easy to go from too short to too long with a nice sharp reamer, goes quick too; don't ask me how I know! Unhappy

Unless it was/is an extremely rare barrel- and I don't know of any;
replacing the barrel is the way to go- if you are not ok with shooting it as is.

As Floyd said, you will have other problems before it becomes "unsafe to fire", JMHO.

Hundreds or thousands of out of spec carbines have no doubt been fired by guys that didn't know about head space, didn't check it, or didn't care. 
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Just curious if the barrel and receiver flats match up.
Also if the Index marks are lined up.

Longer brass wouldn't be supported enough?
Stressing extractor.. ?

Wish there was a workable fix. Seems a shame a good bore will go to waste.

Sorry for all the bad news Col,

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Originally posted by painter777 painter777 wrote:


Longer brass wouldn't be supported enough?
Stressing extractor.. ?

CH-P777

Ruptures in 9mm cases, you bet. I have seen it and read a lot about it. Bulges in the unsupported area of cases is very common, Glocks in particular. I have never heard of, or read about bulged carbine cases, or a ruptured one. If it happens, I think it’s rare....if at all. 

The biggest concern might be bolt-thrust. I have cracked a right lug in a carbine that I knew was long on head space, but it was an N14, so I have to discount that. It might have cracked just because it wanted to.
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