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Discussion Starter #1
I bought this barrel already finished, with the parts kit. The barrel pin groove was already cut. So I press it in the trunnion and find that the bolt won't close on a Go Guage. Did I just buy a fancy tent stake? With the groove already cut, this barrel is no good is it?

This is as far forward at the bolt will go.
 

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What you are experiencing is common when placing a used barrel with a different trunnion and believe it or not you are probably very close to proper head space.

****WHEN CHECKING HEADSPACE USE A BOLT STRIPPED OF EXTRACTOR AND FIRING PIN TO GET PROPER RESULTS****

In your situation you now need to press the barrel forward a tiny bit until the bolt (stripped of firing pin and extractor) will close or nearly fully close on "go" gauge, use a bit of force on the bolt when checking --10-15 lbs pressure. (I used a brass shim/washer and a socket extension and a large hammer to tap my barrels forward a smidge, they jumped a bit to far when using the press).

My factory headspaced rifle will not fully rotate closed on a CIP GO gauge but will fully close on live ammo and functions perfectly. I believe this is due to slight differences in CIP gauges from the Soviet/Euro head space gauges.

On my builds I set headspace the same way, almost fully closed on "go" gauge and reliably closing fully on several brands of ammo. I then take a round (SEE ABOVE NO EXTRACTOR OR FIRING PIN IN BOLT, ACCIDENTAL FIRING OF ROUND HERE WOULD NOT BE GOOD) and put 2-3 layers of scotch tape (.002 thickness per layer) trimmed to fit on the cartridge base and insert it and try to close the bolt on the round...by increasing the layers of tape you can "roughly" see how tight/loose your head space is. I do this as I do not own a no-go gauge and it gives me a idea where I am at. If you can still close it on 4 or more layers of tape I would nudge it a bit tighter.

Too tight a headspace could lead to reliability issues and a possible out of battery firing and to loose and you will get popped/bulging primers, bulged cases, hard extractions and possible headcase seperations so spend a bit of time getting it right.

Once you have it closing or nearly closed on a "Go" gauge and reliably closing all the way on a couple different manufacturers brands of ammo see how far you are off on the barrel channel hole/trunnion alignment. You may just need to then get a oversize barrel pin, redrill and ream the hole oversize and press in the pin.

If you don't want to go ovesized on you barrel pin you could remove the barrel and have someone do a pass or two on the barrel pin channel with a mig welder (no need to fill the whole channel solid with weld) then re-insert barrel and set head space and re-drill pin channel and pin with the original barrel pin.
 

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Is this an AKBuilder kit., pre-assembled barrel unit?
Try a live round and see if the bolt closes on that. It may be a deviation in your GO/NO GO guages vs the originals used to headspace the kit. Generally if it headspaces on a cartridge you are good to go. You can also pin the barrel and then if you have an offset barrel pushing tool you press the barrel with several hundred pounds onto the pin to seat it. This often gives another .001" +/- headspace.
If you are ever so close you can also set the barrel and install the barrel pin. Then you measure each bolt lug front to rear. Note that dimension for each. Gently lap or jeweler file the rear of each lug carefully. Measure and remove a like amount from the rear of each. Stop and check headspace often. Proceed until properly headspaced.
The amount of barrel pin channel overlap will give you a clue on how far off the headspace is to your guages .
 

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Discussion Starter #5
It's not an AK builder kit but it is finished up to the same point that you're referring to. I'm not sure who built it but I know it was a few years ago at least.

So, you guys are awesome. It must have been very close like you described. I took the pin out again and let the bolt slam forward about 20 times. Kept checking the headspace until it would close on a live round. Let it slam a few more times and now it will close on the GO guage! It must have popped the barrel forward just a hair. The pin went back in just fine. So thanks for the info once again!
 

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I would most definitely check it again with a no go gauge after your first, second and third range sessions. Make sure it doesnt loosen up even more. :beer:
 
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