Checking AK Headspacing Before Assembly UPDATES...Constantly happening

[oogabooga]

I have a Yugo M92 2003 parts kit (NOT virgin) and realized it is not numbers matching. The Front Trunnion is 70296 and the Bolt and Carrier are both 70896. Someone may have messed up when matching the kits, I don't know. But that's not the point (though since the numbers are relatively close, it leads me to believe that they were probably built using the same tooling or equally worn tooling). I was wondering if checking headspacing now (Front trunnion still has old receiver tabs riveted in, barrel and barrel pin installed, etc) will give a pretty good idea of how it will headspace when fully assembled. The torched receiver tabs are cut nicely and are not in the way of the bolt or carrier.

I did a quick clean of the barrel and chamber, REMOVED THE FIRING PIN AND EXTRACTOR, and tried chambering with a live round as a GO gauge, and another live round with the 2 layers of scotch tape method as a NO-GO gauge (I don't have my GO and NO-GO gauges with me right now so this will have to do).

With just the bolt, it DOES close on the "GO gauge" and DOESN'T close on the "NO-GO gauge."
With the bolt in the carrier, it also DOES close on the "GO gauge" and DOESN'T close on the "NO-GO gauge."
I even tried using just 1 layer of scotch tape and the bolt DOESN'T close either.

Like most M92 kits, it seems unused. Just covered in cosmoline and possibly test fired. With the kit not assembled, everything seems to check out. Should the build proceed? I'd really like to avoid fixing headspacing.

UPDATE 6/7: Got my GO, NO-GO Gauges back. Post #29

[69Mach1]

I have a Yugo M92 2003 parts kit (NOT virgin) and realized it is not numbers matching. The Front Trunnion is 70296 and the Bolt and Carrier are both 70896. Someone may have messed up when matching the kits, I don't know. But that's not the point (though since the numbers are relatively close, it leads me to believe that they were probably built using the same tooling or equally worn tooling). I was wondering if checking headspacing now (Front trunnion still has old receiver tabs riveted in, barrel and barrel pin installed, etc) will give a pretty good idea of how it will headspace when fully assembled. The torched receiver tabs are cut nicely and are not in the way of the bolt or carrier.

I did a quick clean of the barrel and chamber, REMOVED THE FIRING PIN AND EXTRACTOR, and tried chambering with a live round as a GO gauge, and another live round with the 2 layers of scotch tape method as a NO-GO gauge (I don't have my GO and NO-GO gauges with me right now so this will have to do).

With just the bolt, it DOES close on the "GO gauge" and DOESN'T close on the "NO-GO gauge."
With the bolt in the carrier, it also DOES close on the "GO gauge" and DOESN'T close on the "NO-GO gauge."
I even tried using just 1 layer of scotch tape and the bolt DOESN'T close either.

Like most M92 kits, it seems unused. Just covered in cosmoline and possibly test fired. With the kit not assembled, everything seems to check out. Should the build proceed? I'd really like to avoid fixing headspacing.

yes, go ahead and proceed. It's going to be the same headspacing before and after riveting on th front trunnion. No dim.'s change.

[mrlonewolf]

I would build it. Although check headspace again prior to inserting the barrel pin.

^^^^^ This.

[mydogsmonkey]

make sure that the chamber was clean before you headspaced, i learned that the hard way, kinda haha

[oogabooga]

Thanks, 69Mach, Caiman, and mrlonewolf for the reassurance. I was hoping that would be the answer. I figured I would check headspace again after pressing in the barrel, but I always wondered why people said to check headspace after damn near most of the gun is assembled as opposed to right when you get the kit.

Haha, yes, mydogsmonkey. I did clean the chamber prior to checking headspacing. Thanks for the reminder, though. That chamber was dirty as sin when I got it, but one pass through with a bore brush and a patch, and it's clean enough for me!

This is just the most expensive kit I've bought and I want to be for damn sure it works in the end. Call me cautious, but I like the reassurance from people who've built a few more AK's than I have

If anyone else has any input, comments, concerns feel free to share.

[oogabooga]

So someone over at another forum expressed his concern about using a live round as a headspace gauge since the tolerances of a live round do not equal that of a GO, NO-GO gauge. This holds some water in my mind, and the scotch tape method seemed janky enough as it is. I do have GO, NO-GO gauges, but I won't have access to them for a handful of days. I'll hold my breath and pray they work out for me.

But for now, my main concern at hand is determining whether or not headspacing PRIOR to assembly is an accurate representation of headspacing AFTER assembly as described in the original post. I'm not saying 69Mach1 is wrong, because what he says makes complete sense to me: that headspacing before assembly should be damn near equal to headspacing after assembly. The bolt locks into the front trunnion and against the barrel, and locking is only contingent on the front trunnion and barrel (as opposed to other parts added during assembly such as the receiver, FCG, etc). So it doesn't even touch anything else besides the carrier. And assuming I use the same barrel/barrel-pin/barrel-pin-hole position that the disassembled kit currently is in, the bolt should lock up exactly the same when assembled.

The reason I'm losing sleep over this (jokes...kinda...) is that the same guy who brought up that a live round is not an accurate GO Gauge also said that headspacing can't be checked before assembly. Yes, after assembly would be the most ideal time to check for headspacing, and I will indeed check headspacing after I build it up. But the only reason so far I've run across that would make this method of checking headspacing inaccurate is sheering of the barrel pin during its installation. What else could potentially cause problems in regards to the headspacing being altered before and after assembly?

[oogabooga]

Some combloc rounds are better than the SAAMI guages in my view. The specs are different. I've tried the SAAMI guages on matching kits (still assembled) and at times they do not close. This was on the GO gauge. Put in an inert round and it closes. So the logic - SAAMI are made to US specs. The AK is made to Combloc specs as well as the ammo that will be used. Several matching kits just wouldn't close on the Go guages so when I tried Wolf, Brown Bear, Yugo it closes.
You check headspace (HS) beforehand to insure that you can work with your kit. It is correct that the final check after assembly is the most important. When you do press your barrel back in, it needs to line up exactly in the hole. That's usually not the case, so you sort of have to push in or back out just a tiny bit, HS again and adjust. Only after your HS comes back correctly than you push the pin in. Sheering of the pin during reassembly occurs when the holes are not perfectly lined up and can affect the headspace. That is why the barrel pin is inserted after checking HS and once inserted rechecked.


If your in So Cal (LA area). I can show you in person to put you at ease.

Yea, I've experienced similar results with my manson reamer CIP GO and NO-GO gauges. My matching kit Romy G build didn't close on either of them. But like what you suggested, people said as long as it doesn't close on the NO-GO, and it locks in on a live round, it should be good to go. A lot of good info (for me at least) in that post. You seem to know what you're talking about so I'll take your word for it

I'll wait a few days till I can get a hold of my CIP gauges again and see how well those lock up. Is there a way to prevent sheering of the barrel pin other than the good 'ol fashioned, scientific method of eye-balling? That's what I did on my last build, but I never thought of it before.

[Z ME FLY]

Yea, I've experienced similar results with my manson reamer CIP GO and NO-GO gauges. My matching kit Romy G build didn't close on either of them. But like what you suggested, people said as long as it doesn't close on the NO-GO, and it locks in on a live round, it should be good to go. A lot of good info (for me at least) in that post. You seem to know what you're talking about so I'll take your word for it

I'll wait a few days till I can get a hold of my CIP gauges again and see how well those lock up. Is there a way to prevent sheering of the barrel pin other than the good 'ol fashioned, scientific method of eye-balling? That's what I did on my last build, but I never thought of it before.

Pretty much eye ball it, clean out the barrel pin hole with a qtip. Use a scribe or center punch and run it in the hole to see if there is any of the lip left of the barrel pin hole.

[Z ME FLY]

Two additional things I should mention. The first one and this is very important. It should go without mentioning, but I'll do it anyway. If your going to use a live round be very extremely careful. Remove the firing pin and go very slow. Point the barrel at a safe object. Safety first. Second is that I made an error in my post. It is not the barrel pin that sheers. Rather is stays in line and will 'shave' the barrel itself. You'll sometimes see a bit of barrel shaving after pressing in the pin. This occurs since the pin is harder than the barrel material and the barrel is not in line with the trunnion hole. Very common.

Z Me Fly is correct on the process. I would add to use lots of light so you can clearly see through the hole.

Yes light is your best friend, forgot to add that. If it shaves the barrel pin hole a bit, probably not a huge problem but you want to have it as least as possible.

[oogabooga]

Two additional things I should mention. The first one and this is very important. It should go without mentioning, but I'll do it anyway. If your going to use a live round be very extremely careful. Remove the firing pin and go very slow. Point the barrel at a safe object. Safety first. Second is that I made an error in my post. It is not the barrel pin that sheers. Rather is stays in line and will 'shave' the barrel itself. You'll sometimes see a bit of barrel shaving after pressing in the pin. This occurs since the pin is harder than the barrel material and the barrel is not in line with the trunnion hole. Very common.

Z Me Fly is correct on the process. I would add to use lots of light so you can clearly see through the hole.

Yup! Safety first. As stated in my original post, firing pin and extractor have been removed, and all chambering was done with the muzzle pointed in a safe direction. Thanks for looking out, though. Can never be too careful. I did not know that the barrel was a softer metal than the pin. I would have figured it was the other way around. Good to know.

Pretty much eye ball it, clean out the barrel pin hole with a qtip. Use a scribe or center punch and run it in the hole to see if there is any of the lip left of the barrel pin hole.

Ahh yes. That sounds like a crude, yet effective way of making sure the barrel lines up with the hole. Better than only eyeballing it.

Thanks for the tips, guys. Keep'em coming. Especially like the ones above about making sure the barrel is installed properly to maintain correct headspacing.

[Z ME FLY]

Yup! Safety first. As stated in my original post, firing pin and extractor have been removed, and all chambering was done with the muzzle pointed in a safe direction. Thanks for looking out, though. Can never be too careful. I did not know that the barrel was a softer metal than the pin. I would have figured it was the other way around. Good to know.



Ahh yes. That sounds like a crude, yet effective way of making sure the barrel lines up with the hole. Better than only eyeballing it.

Thanks for the tips, guys. Keep'em coming. Especially like the ones above about making sure the barrel is installed properly to maintain correct headspacing.

Haha it's crude but it's pretty much the only way I have seen it done. Just make sure you grease it or lube it a bit but don't go overboard with the lube. Go slow, the bigger PIA is making sure the barrel is straight in the trunnion so it will clear the ears.

You can always freeze the barrel too if you need help pressing it in.

[oogabooga]

Haha it's crude but it's pretty much the only way I have seen it done. Just make sure you grease it or lube it a bit but don't go overboard with the lube. Go slow, the bigger PIA is making sure the barrel is straight in the trunnion so it will clear the ears.

You can always freeze the barrel too if you need help pressing it in.

I remember way back when I did my RomyG build, i got the ears to clear the trunnion, but it was slightly canted (as in if you were to look down the sights, the whole barrel assembly would be rotated counter clockwise by a few degrees). I was using the All-Thread method and the rotational motion of tightening the nut to press the barrel in must have rotated the whole assembly slightly. But even though it was canted, I just pounded the barrel pin in, and the barrel eventually corrected itself. I believe I eyeballed it so there was no lip, but I was still pounding the pin against the canted barrel. As in the barrel pin was pressing in on the bottom of the "U" of the barrel notch. (Wow this is hard to describe without pictures haha).

Would doing this method of "correcting" the cant in the barrel damage the barrel or cause there to be shavings of the barrel come off? I can imagine the "U" of the barrel notch and the "O" of the trunnion hole being misaligned and having shaving occur in that instance of misalignment. But does what I did in the previous paragraph with the canted site also cause damage? I'd assume it's not preferable, but as long as the damage is negligible, I can live with it

[CEDaytonaRydr]

American Firearms Customer to Russian AK builder:


American: Did you check the headspace on this rifle?

Russian: What is this "headspace" of which you speak?

[oogabooga]

American Firearms Customer to Russian AK builder:


American: Did you check the headspace on this rifle?

Russian: What is this "headspace" of which you speak?

Named after the space cleared out in your head when you shoulder an American Bubba'd rifle that hasn't been "headspaced." Hence the term.

Besides. In Russia, you just go down to the Ruble store, or trade in your water, and pick up a new one that's been headspaced at the factory. No need to do this kit building business

[Z ME FLY]

I remember way back when I did my RomyG build, i got the ears to clear the trunnion, but it was slightly canted (as in if you were to look down the sights, the whole barrel assembly would be rotated counter clockwise by a few degrees). I was using the All-Thread method and the rotational motion of tightening the nut to press the barrel in must have rotated the whole assembly slightly. But even though it was canted, I just pounded the barrel pin in, and the barrel eventually corrected itself. I believe I eyeballed it so there was no lip, but I was still pounding the pin against the canted barrel. As in the barrel pin was pressing in on the bottom of the "U" of the barrel notch. (Wow this is hard to describe without pictures haha).

Would doing this method of "correcting" the cant in the barrel damage the barrel or cause there to be shavings of the barrel come off? I can imagine the "U" of the barrel notch and the "O" of the trunnion hole being misaligned and having shaving occur in that instance of misalignment. But does what I did in the previous paragraph with the canted site also cause damage? I'd assume it's not preferable, but as long as the damage is negligible, I can live with it

It is shootable still and not a problem, you just want to make sure you hardly save any of the barrel pin hole off. If you think about it the difference of .005 is no go and go so there is a little room for play but not a lot.