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Old February 18, 2013, 07:28 PM   #1
GunXpatriot
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How to check headspace on SKS?

So I've been searching everywhere I can't really find any information on this. Very frustrating. I remember reading a thread somewhere that said something like "It's not the bolt carrier you need to look at, it's the bolt itself" and the guy's headspace was fine to begin with, etc. What exactly am I looking for when testing this? I know on a Mosin Nagant, you need to remove the extractor, or at least you do to my knowledge. What is the prep for headspacing an SKS?

I also hear that there are gauges with the extractor cut into them, so it won't have to be removed. Would anyone know where I could find (hopefully) a full set of Go, No Go, and Field? I'm also looking for something like this for my Mosin-Nagant, preferably with the extractor cut.

I was looking on Brownell's and seen a Go/No Go set for both 7.62x39 and 7.62x54r. Manson gauges, which in the picture had the extractor cut in the picture for .45 acp, but it doesn't specify if they are cut for all of the different chamberings. From what I hear these gauges are very good.

http://www.brownells.com/gunsmith-to...prod25181.aspx

I've also found a 7.62x54r field gauge at the bottom of this page.

http://www.brownells.com/gunsmith-to...prod19183.aspx

If I have to wind up removing the extractor to test the field gauge if I need to, that's fine. As for the SKS, depending on the pre for testing, I can get either the Cylmer or Manson. If the extractor is easy to remove I'll just go for the cylmer for 5 bucks less. What I can't find is a field gauge for 7.62x39. What if the Go/No Go aren't sufficient?

Honestly, this is all really aggravating, and I've called most of the people in the area. None of them have gauges I can have them test with, let me borrow or rent, etc. If it helps, I bought my Mosin-Nagant from AIMsurplus, which I assume tested the gun before sending it out, but there is no guarantee... The thing I need the most info on is how to test the SKS though, sorry for writing a novel. Honestly, I think I'm done with surplus guns... Extremely aggravating...
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Old February 18, 2013, 07:30 PM   #2
Jim Watson
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Why do you need to measure the headspace on an SKS?
Are you getting casehead separations of the usual Com-bloc surplus?
Do you reload for it?
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Old February 18, 2013, 07:46 PM   #3
GunXpatriot
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No, I'm just afraid to shoot the thing before testing. The bolt isn't matching which made me want to check it. Like I said, I haven't even shot the thing yet, so no.
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Old February 25, 2013, 02:19 PM   #4
.50cal packer
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As far as your mosin goes, use these. You dont have to remove the extractor.
http://firewerks.net/shop/firewerks-headspace-gauges/

Now, I haven't seen a field gauge for the SKS. Doesn't mean it's not out there. If you're serious about being done with the C&R life, I wouldn't bother with buying Any gauges for it. With a couple more purchases of SKS's, it would be beneficial. If this is your last one ever.... Then just take it to a smith, who more than likely, has the gauges and they'll give it a once over for your safety. It's better that they do it, because they know what they're doing. Even if you found a field gauge, you could still mess it up, and end up with an unsafe gun.
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Old February 25, 2013, 03:07 PM   #5
iraiam
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You need a standard set of 7.62X39 head space gauges (go and no-go), these will be more costly than the mosin gauges because 7.62X39 head spaces of the case shoulder, which requires more complex machining to make.

Your best bet would be to take it to a gunsmith, unless like previously posted, you want to collect these rifles and can justify the cost of the gauges.

Also, checking head space on a semi-auto is more complex than a bolt action, The bolt needs to go into battery properly with the go installed, and must not go into battery with the no-go installed, and must not fire out of battery.
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Old February 25, 2013, 04:55 PM   #6
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Actually, unless it's a brand new gun, you want the FIELD rather than the NO-GO. The former determines end of service life, while the latter is used in cutting the chamber. There is no fixed SAAMI standard for NO-GO. It's just the gage maker's best guess as to how tight a newly cut chamber should be.

Commercial gages pretty much always have an ejector space groove cut in to them these days. The extractor should not be an issue as it just goes in the gage extractor groove. These gages are strong, and you can stretch a chamber camming one in with the locking lugs, so you want the bolt free and not under recoil spring force.
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Old February 26, 2013, 01:41 PM   #7
iraiam
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I disagree, a field gage is used to test the absolute limit in chamber depth. I personally would not fire a weapon that failed the no-go gage test unless I needed it in a life and death situation. IMO, an SKS that goes into battery on a no-go gage should be considered unsafe, as we are not talking about an actual service weapon, although it may have been formally.

Since the 7.62x39 is a rim-less case which head spaces between the bolt face and the case shoulder, I doubt that a "FIELD" gauge will be easy to come by.

I've got 2 Mosin rifles, Chinese SKS, M1 Garand. I've never used a field Gage on any of them, just the go/no go.
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Last edited by iraiam; February 26, 2013 at 02:05 PM.
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Old February 27, 2013, 11:10 AM   #8
Unclenick
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Iraiam,

The information I gave was correct as to how the standards are set up to work. If you have a personal standard that says a used gun with mismatched bolt has to have headspace as good as that of a newly chambered rifle, that's your personal choice. It's just not how the standards are set up.

As far as SKS safety, or that of any other self-loader with a floating firing pin goes, it seems to me extra headspace makes more room for the case to move the primer away from the firing pin and less likely it would meet resistance to chambering as the bolt closed. So, if anything, it would reduce rather than increase slamfire likelihood. If you are worried about how a couple of thousandths will affect pressure ring stretch in the case, then you resize for the chamber. For disposable brass in new ammo it should be no concern at all. Look at Hatcher's description of an experiment with a chamber moved 50 thousandths forward on purpose. It had no case failure issues (though I sure wouldn't try to reload a case stretched that far). So I don't see how safety would be adversely impacted by having a chamber that meets the standard requirements.

My first Garand came from the DCM with a chamber 0.007" over minimum, which is 0.001" over Clymer's NO-G0 for .30-06 of 0.006" over minimum (some companies make 0.005" over as NO-G0) and 0.003" under FIELD. After bedding, the first group out of it from prone position put 10 rounds into 0.7" CTC. With the sizing die set up to push shoulder's back two to three thousandths it did just fine on brass life, too, and lasted another 2,000 rounds before it was shot out. Nary a problem. You just have to load for the gun.
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