[bullet175]

Ive got several ?s here to ask about headspacing an AK and headspacing in general.

First off ......A rifle must be headspaced and it is either right or it is not. If this is true then why do we use three different guages, field, go and no-go. Would you not use just one guage and get that one right? Or is the goal to get the bolt to fit somewhere between the go and no-go guages?

Next....When you headspace an AK do you do it by moveing the barrel in or out of the trunnion until the bolt will lock down on the correct guage?... or tweek the lugs of the bolt to get the same if its too tight? And if its too loose would you move the barrel back a tad and the re drill the barrel pin hole for oversized pin?

These are just some things I have been tossing around in my brain bucket for some time. I did a search but really coulnt find what I was looking for. I know this headspacing is not rocket science but im kind of baffled. Im planning on buying some guages soon. What type should I buy for the AK ? Thanks

 

[scubadvr]

I got a set of guages from Brownells. (go and no go) Basically, a bolt should close on a "go" guage. It should not close on a "no go". Note, I said should not close. In some weapons like a FAL, it is permissable to use a weapon that the bolt closes on a "no go". However, it must never close on a "field" guage. That being said, most guys use only the two guages "go" and "no go", becase it is a safety factor.

Regarding headspacing an AK. The head spacing is done for you if you purchase a kit with a matching barrel and trunion. Thats because when they are manufactured, head spacing is set then the barrel and trunion are drilled and pinned. It is all together possible to get a barrel and trunion that were not from the same weapon and the headspacing will be off. As a rule I will not purchase a trunion and barrel separately. I want them from the same weapon. If you have a weapon that the bolt closes on a "no go" it can be tightened by using an oversized barrel pin which can be a real pita.

I hope this helps, its my understanding, and I am not a gun smith and do not play one on T.V. Jack

 

[sks_hunter]

I hope this helps, its my understanding, and I am not a gun smith and do not play one on T.V. Jack

But, did you, in fact, stay at a Holiday Inn last night?:lol:

From my discussions with hotbarrel, my understanding is that, if the headspacing is more than just a couple of thousandths off, you could be in for some work, since this is all that an oversized pin will give you. If it's off more than what the bigger pin will make up, you might in fact be forced to fill the barrel notch in with weld, and turn it smooth on a lathe, then insert to proper depth, and redrill the barrel through the existing holes in the trunion. this could actually work well, and allow you to be right on the money. I totally can agree to the matching barrel and trunion... there ain't no slop to play with, and if you get the pin back in after removing, you know you're right back on the money.

 

[bullet175]

The thing is Ive got some extra barrels trunnions and bolts (non matching) that I got in bummer parts kits. I wound up canablizing the good stuff from the parts sets and now I have enough extra stuff that I could accually build 2 or 3 mutt AKs out of. I just need to learn how to headspace if I plan to use the parts. Ive thought of the possibility of haveing to weld up barrel groves but that wouldnt be a big issue for me. What I really need is a bending jig for my flats. Ive got three nice sets that are ready to mount as soon as I get a jig. Im just waiting on Bamasam to go into production.

 

[Trotsky]

"The head spacing is done for you if you purchase a kit with a matching barrel and trunion"

Pay close attention to this. Some cheap kits may NOT have matching parts... it's a good idea to check headspace on "matching kits".

 

[scubadvr]

Or even better on any build, no every weapon you use. Jack

 

[tac-40]

First off ......A rifle must be headspaced and it is either right or it is not. If this is true then why do we use three different guages, field, go and no-go. Would you not use just one guage and get that one right? Or is the goal to get the bolt to fit somewhere between the go and no-go guages?

The head space gauges are
GO

NO-GO

FIELD

The Go gauge is the minimum headspace allowable. The bolt must be able to close on the GO gauge. This is to make sure that all ammo of that caliber specifications will chamber without creating a dangerous situation, such as crushing a case, or forcing the neck into the rifling. The NO-GO guage is the maximum headspace allowable for a normal weapon. The bolt should not close on the NO-GO gauge. This is to make sure that all ammo is properly supported to prevent case ruptures and blowouts. The field gauge is the absolute maximum that the headspace can be. The bolt should never close on a FIELD gauge. If the field gauge specs are exceeded the weapon MUST be removed from service and not fired until repaired. The field gauges are typically used for fully automatic weapons. I don't ever recall seeing a field gauge for a non-military caliber.

Headspace does affect accuracy and reliability. Too much headspace allows to bullet to move a bit before engaging the rifling meaning there is no consistancy between shots. Too small head space can lead to failure to feed and eject issues because of the tight chamber.

I would get a GO and NO-GO gauge and make sure that your rifle's headspace is between the two. No need to get a Field gauge unless you just want it. Check this forum for more info about setting headspace.

 

[hotbarrel]

I know I am crazy but I am looking forward to the new chalanges of head spaceing a totaly miss matched set.
bullet 175 If you can press in and out easy then I would press one togeather and line up the pin hole and check the space, nouthing to loose if you can press easily. heck maby take some measurements and try another trunion on the same barrel. try differant bolts with each set up. maby you will luck out rite?? if you find a set up that spaces out then put in a pin.
it is not recomended to grind the bolt to alter space, the best thing is to move the barrel in or out. as mentioned above an oversize pin is onle a TINY bit bigger so if you are off by more than a couple thousandths it will not help. filling the barrel and redrilling after it is positioned is required. maby if you are very good with machine tools you can but a trunion with no holes at all and drill new holes in the trunion and hit the notch in the barrel exactly , but boy that would require something better than a $29 drill press from discount tool barn.

 

[sks_hunter]

global has new undrilled trunions...

 

[Rhino_66]

You can also order drill rod and properly sized reamers for making your own oversized pins. As long as you don't break through into the chamber you should be fine.

 

[7.62x39]

Another vote for always checking.
My AMD65 kit was all matching numbers, yet it swallowed my no-go guage.
I used a drill bit shank for a pin.