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Old 02-17-2017, 03:13 PM   #1
ak mike
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Default AK74 head spacing virgin barrel

Bought a kit sometime ago and it came with virgin barrel. Have pretty much all the necessary tools to start (go, no-go gages and unfired round) and for safety purposes I removed firing pin. Also have info on how to popularize a virgin barrel. I've followed instructions which I read numerous times , so I began the process .
1. Barrel journal and front trunion within .001-.002
2. Cleaned and lubed both barrel and trunion
3. Clocked extractor cut outs at 11:00 and 4:00 positions and proceeded to press barrel in .
4. Measured 3/16" from bottom of triangular part of bolt lug to top right of right rear of trunion. (With go-no gage)
5. With Go gage used it feels loose
6. With live round have slight drag but no bind and of course as I mentioned no firing pin for safety. But round has no problem seating fully but can rock the lug a bit.
Being that this is my first virgin barrel to populate.
Can anyone give me a few tips if I'm going the right direction ? Much appreciated.
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Old 02-17-2017, 03:27 PM   #2
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Proper way to head space is to disassemble the bolt completely...I am guilty of not doing that but its the correct way.

And forgive me, but I dont understand what #4 is describing?

Someone else will be here shortly to post on the ft/lbs of force required to close the bolt on a gauge and other tid bits.
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Old 02-17-2017, 03:58 PM   #3
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Me personally, I'd get a field guage too. If it swallows a field, you must re space. Having 3 measurements is a great way to ensure correct spacing.
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Old 02-17-2017, 04:25 PM   #4
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If it won't close on a no-go you have no need for a field gauge
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Old 02-17-2017, 04:27 PM   #5
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Take a picture of the bolt with it closed on a go-gauge, and closed on the no-go. Also try it with the carrier, should take a little push to send it home on go, and shouldn't close on a no-go.
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Old 02-17-2017, 09:35 PM   #6
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Much appreciated for the info , as for #4 let me reword that , but first let me clarify , as of right now my front trunion is not riveted onto receiver, my info is from the book ," how to build a AK volume1 head spacing and barrel populating", when using go-no gauge top rear of bolt ( I mentioned lug) is triangular , the gap when closed between the triangle and trunion edge should roughly be 3/16" in. , when I use go gauge it feels a slight loose , and with a live round (no firing pin) it's snug but I can rock the bolt a bit . I will be purchasing field gauge shortly , good advice , best to check all three areas. Is there something I'm doing wrong?
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Old 02-18-2017, 09:50 AM   #7
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it seems a little loose to me by what you described. but again, field guage measures whether its just "worn in setting" or "wore out setting". when you use carrier with nogo, how close is it to your trunnion? how big is that gap. i use bolt by its self first to space, and also use bolt and carrier just to make sure when measuring all that.
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Old 02-18-2017, 09:59 AM   #8
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It should be very tight/almost non-closable on a go gauge and it should not even come close to closing on a no go. With it very tight on the go gauge it will still close easily on a round. Any other measurement you are doing with trunnions and whatever is pointless.
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Old 02-18-2017, 10:32 AM   #9
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Quote:
Originally Posted by def90 View Post
It should be very tight/almost non-closable on a go gauge and it should not even come close to closing on a no go. With it very tight on the go gauge it will still close easily on a round. Any other measurement you are doing with trunnions and whatever is pointless.
Of the same opinion here. Tighten up.
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Old 02-18-2017, 07:30 PM   #10
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Quote:
Originally Posted by def90 View Post
It should be very tight/almost non-closable on a go gauge and it should not even come close to closing on a no go. With it very tight on the go gauge it will still close easily on a round. Any other measurement you are doing with trunnions and whatever is pointless.
This. ^^^^


Stripped bolt, put the go gauge in the chamber, put the bolt in the carrier and push on the back of the carrier, 0 to 33 lbs of force to cause it to close are the acceptable specs. I prefer to have to use about 25lbs or a bit more to get it to close. It will snap into place once you have enough force on it.
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Old 02-18-2017, 08:18 PM   #11
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Quote:
Originally Posted by ak mike View Post
Much appreciated for the info , as for #4 let me reword that , but first let me clarify , as of right now my front trunion is not riveted onto receiver, my info is from the book ," how to build a AK volume1 head spacing and barrel populating", when using go-no gauge top rear of bolt ( I mentioned lug) is triangular , the gap when closed between the triangle and trunion edge should roughly be 3/16" in. , when I use go gauge it feels a slight loose , and with a live round (no firing pin) it's snug but I can rock the bolt a bit . I will be purchasing field gauge shortly , good advice , best to check all three areas. Is there something I'm doing wrong?
Are you sure you want to headspace before you rivet the trunnion in place?
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Old 02-18-2017, 08:46 PM   #12
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There is no need to rivet in the trunion or use the carrier to set head space.

If the bolt closes on the go and dosent on the no go it's in spec for a newly built rifle.

Most guys want to set there rifles up snug on the NO GO
for best accuracy.

If your going to do head space with a carrier there are actually some other steps you should do first to insure lug contact is true.

IMO needing 33 pounds to close a action is crap and a builder should do better.

It's pretty simple .
Bolt closes on a Go guage slight friction is OK
Bolt dosent close on a NO GO guage.
There is no need for a Field guage on a build.that's for checking if a used rifle is still safe.
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Old 02-20-2017, 11:25 PM   #13
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Thanks for much needed info , I will snug it up , I didn't feel to comfortable too loose . With the right tools and info , I'll get it done safely , and be able to use it safely. Thanks again
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Old 02-21-2017, 03:23 PM   #14
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Success with carrier and go gauge it took some effort to close I estimate around 20-25 lbs , with carrier and no-go gauge it would not close. Also tried without carrier closed with go gauge and would not close with no-go. Thanks everyone for your input.
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