tighten ak gas piston


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callo685
November 24, 2008, 02:51 PM
Whats the best way to tighten the gas piston of an AK into the bolt carrier?
I have a WASR 10 if it makes a difference.
Thanks

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BornAgainBullseye
November 24, 2008, 03:04 PM
leave it loose. That is the way God intended it to be. Tighten it and it may bind up in the gas tube, as they do not perfectly align

Ian
November 24, 2008, 03:07 PM
Yep, they are supposed to have some wobble. Doesn't work well if it's tightened down solid.

expvideo
November 24, 2008, 03:12 PM
+1. It's called "loose tollerances" and it is what creates that well known AK reliability.

Ian
November 24, 2008, 05:28 PM
Just to be nit-picky...it's a loose clearance, not a loose tolerance. Tolerance is how much a finished dimension can vary from what the blueprints call for, while clearance is the spacing between components that fit together. Loose clearances (among other things) make the AK reliable - loose tolerances just mean poor quality control at the factory.

dfariswheel
November 24, 2008, 07:58 PM
Some AK's have loose gas pistons, some have tight pistons.

If the rifle works properly..... leave it however it is.

Sam1911
November 24, 2008, 08:14 PM
And just to add a reinforcing point:

If it bugs you so much you just can't resist tightening it... just DON'T do it!

There's a pin -- sort of a long rivet, actually -- that runs horizontally through its threaded section. If you get a hold of it with a pipe wrench and vice to try and force it, you will eventually break something. (Probably shear off the pin.) Whatever gives will be a pain in the neck to replace.

If you're looking to replace the gas piston for sec. 922r compliance reasons you will have to buff or lightly grind the finish off the front 3/4" or so of the carrier where the piston screws in until you can see just where the head of that pin is. Then you'll need to center-punch the head and drill it off. (Don't go too far, the pin is only about 1/8" dia., but the head will be peined out to more like 1/4" dia.) Afterward you can tap the shaft of the pin out with a punch. You'll, of course, need to have a replacement pin on hand to put it back together securely.

And, make sure you DON'T screw the new piston in any tigher than the old one was before you drill your new retaining pin hole through it. As said before, most have some play...they're supposed to.

-Sam

Eagles6
November 24, 2008, 08:18 PM
If it ain't broke, don't fix it. They are supposed to be loose. If the rifle shoot leave it alone.

nalioth
November 24, 2008, 08:48 PM
If you're looking to replace the gas piston for sec. 922r compliance reasons you will have to buff or lightly grind the finish off the front 3/4" or so of the carrier where the piston screws in until you can see just where the head of that pin is. Then you'll need to center-punch the head and drill it off I can go one better.

Polish both sides of the bolt carrier and use a punch on the small end of the rivet.

No drilling needed.

callo685
November 24, 2008, 10:51 PM
awesome i had no idea. i thought it was messed up Thanks

Thin Black Line
November 25, 2008, 08:07 AM
leave it loose. That is the way God intended it to be. Tighten it and it may bind up in the gas tube, as they do not perfectly align

and

Yep, they are supposed to have some wobble. Doesn't work well if it's tightened down solid.

and

They are supposed to be loose.

Doncha love the internet?

My very accurate Bulgarian has a nice tight piston. In fact, every one of
the original factory-built AKs (not CAI garage compliance re-builds) I've used
all had nice tight pistons. Yes, and I recall that Chinese AK which had a PIN
all the way through the piston and bolt carrier.

Gee, sounds like they're suppose to be tight rather than loose. ;)

That said, it probably won't hurt it if it's a little loose and it probably won't
back all the way out of the threads. And it probably won't affect your
accuracy all that much. Not enough for the average AK shooter using it
on milk jugs at 25 yds.

expvideo
November 25, 2008, 09:18 AM
My very accurate Bulgarian has a nice tight piston. In fact, every one of
the original factory-built AKs (not CAI garage compliance re-builds) I've used
all had nice tight pistons. Yes, and I recall that Chinese AK which had a PIN
all the way through the piston and bolt carrier.

Gee, sounds like they're suppose to be tight rather than loose.
Sounds like someone doesn't know what he's talking about. My very nice custom built Polish AK has some wiggle in its factory original piston. Some do, some don't. That is how it is supposed to be. Leave it as it is.


That said, it probably won't hurt it if it's a little loose and it probably won't
back all the way out of the threads.
...Because it's pinned with a rivet. You're really starting to sound like an expert.


And it probably won't affect your
accuracy all that much. Not enough for the average AK shooter using it
on milk jugs at 25 yds.
Not at all actually. The looseness or tightness of your piston will have absolutely zero effect on accuracy. The fact that you would mention accuracy kind of shows how much you know on the subject. "i've handled a few AKs" does not make you more knowledgeable than the rest of us. I happen to know a lot about AKs, and I can tell you with absolute certainty that the piston is supposed to have a little bit of wiggle. I can also tell you with absolute certainty that the wiggle does not effect accuracy at all. Not a little. Not at all. None. Nada.

callo685
November 25, 2008, 11:24 AM
I think I'm gonna leave it as is. I was just worried about but now I know where to go first when I'm not sure about something

Thanks again

Hoppy590
November 25, 2008, 11:37 AM
+1. It's called "loose tollerances"

clearances, not tolerances :)

BornAgainBullseye
November 25, 2008, 12:09 PM
If you look close where it threads in, you will see a small circle that has been filled and sanded smooth. This is where the pin is. The piston will not "back out" These AKM's are built loose for a reason. Mabye a high end Milled Russan or US made AK made to exact specs and gasblock and barrel and all of the sort are perfectly aligned... Then you can have a tight piston. In your case it would prob bind up on the gas tube. If you look really close you may notice that your front sight or gas block may be misaligned slightly. I have seen this in almost every Romanian AKM. This is one reason they leave it loose. It will make no better by having a tight piston verses a loose one. Other than function when your tight one binds up and causes a stoppage

expvideo
November 25, 2008, 12:31 PM
clearances, not tolerances
Actually in the case of AKs it's both. But you're right. I meant clearances.

Thin Black Line
November 25, 2008, 12:46 PM
Someone miss their morning coffee today? Clearly, we need to tolerate it. ;)

expvideo
November 25, 2008, 01:59 PM
Someone miss their morning coffee today? Clearly, we need to tolerate it.
Pardon my tone, but I don't appreciate being painted as an armchair expert while you give incorrect information to the OP.

WardenWolf
November 25, 2008, 02:11 PM
The piston does NOT have to have wobble to it. I've got 2 that are solid as a rock. The carrier and gas piston might as well be a single piece on both my Saiga and Romak-3. The best fix in your case, since the piston was obviously installed poorly and is already tapped at a point where it's loose, is to remove it and buy a new AK gas piston, then install it so it's tight. US-made pistons are widely available and cheap, so it's not a big deal. It is probably a very good idea to have this done, as a piston with play on it will find leverage against the pin that is supposed to anchor it, and the pin will eventually suffer metal fatigue and break. The carrier might also suffer some damage in the process.

Incidentally, the use of a US-made piston will also give you a 922(r) compliance part.

nalioth
November 25, 2008, 02:29 PM
a piston with play on it will find leverage against the pin that is supposed to anchor it, and the pin will eventually suffer metal fatigue and break. The carrier might also suffer some damage in the process. Ummmmkay.

The piston is threaded into the bolt carrier.

The piston has a hole drilled in it that coincides with holes in the bolt carrier.

The piston has a rivet run though it which extends out past the sides of the bolt carrier that has been peened and polished into place.

What "pin" are you talking about breaking off?



If you look at the design specs, they're supposed to be slightly floppity.

expvideo
November 25, 2008, 02:33 PM
The piston does NOT have to have wobble to it. I've got 2 that are solid as a rock. The carrier and gas piston might as well be a single piece on both my Saiga and Romak-3. The best fix in your case, since the piston was obviously installed poorly and is already tapped at a point where it's loose, is to remove it and buy a new AK gas piston, then install it so it's tight. US-made pistons are widely available and cheap, so it's not a big deal. It is probably a very good idea to have this done, as a piston with play on it will find leverage against the pin that is supposed to anchor it, and the pin will eventually suffer metal fatigue and break. The carrier might also suffer some damage in the process.

Incidentally, the use of a US-made piston will also give you a 922(r) compliance part.

Most US pistons will be a tighter fit and therefore have less wiggle. The gun is designed to have a little wiggle. Getting rid of the wiggle may or may not hurt the gun. That depends on how the gun was manufactured, since gas blocks are usually slightly canted. this is normal. The wiggle is not a problem, and replacing the piston is not an improvement on reliability. At best it will do nothing, and at worst it will cause your gun to jam.

WardenWolf
November 25, 2008, 02:35 PM
What you're calling a rivet, I'm calling a pin. Not a huge difference. At any rate, what's happened in his case is the gas piston was not threaded all the way to the rear before being drilled and riveted. Or something was made slightly out of spec. Either way, I'd get it fixed because you want the line of force to be entirely on the threads, with the rivet / pin just keeping it from turning. You don't want the rivet or pin to be absorbing the recoil energy.

expvideo
November 25, 2008, 02:43 PM
What you're calling a rivet, I'm calling a pin. Not a huge difference. At any rate, what's happened in his case is the gas piston was not threaded all the way to the rear before being drilled and riveted. Or something was made slightly out of spec. Either way, I'd get it fixed because you want the line of force to be entirely on the threads, with the rivet / pin just keeping it from turning. You don't want the rivet or pin to be absorbing the recoil energy.
It seems to work for all of the non-US piston AKs out there.

elmerfudd
November 25, 2008, 03:07 PM
I find this to be a somewhat interesting topic.

Some on here have claimed that having either a loose or tight piston will have no effect on accuracy. Considering that anything rattling around or moving that has any contact with the barrel will affect accuracy, I find this questionable. Maybe the effect is slight, but I'm betting that one is better than the other when it comes to accuracy.

My guess would be a that a tight piston would probably produce better accuracy in a gun where the gas block and trunnion were perfectly aligned. It just seems to me that less variation and slop would be more conducive to accuracy.

I haven't done any testing though, so maybe it's the other way around. I know that CampyBob suggests a loose fitting gas tube for best accuracy.

nalioth
November 25, 2008, 03:28 PM
What you're calling a rivet, I'm calling a pin. Not a huge difference. At any rate, what's happened in his case is the gas piston was not threaded all the way to the rear before being drilled and riveted. Or something was made slightly out of spec. Either way, I'd get it fixed because you want the line of force to be entirely on the threads, with the rivet / pin just keeping it from turning. You don't want the rivet or pin to be absorbing the recoil energy.Ask any AK builder out there who's worth his salt, and I'd say the vast majority of 'em screw their pistons all the way in and then unscrew them 1/4 to 1/2 turn before drilling and riveting them.


You are entirely correct in that "the gas piston was not threaded all the way to the rear before being drilled and riveted."

This is how it's supposed to be.

Considering that anything rattling around or moving that has any contact with the barrel will affect accuracy, The gas piston doesn't contact the barrel.

All the function of the gas piston is taken care of entirely inside the gas block. The gas tube is just there to guide the gas piston into the gas block.

If the gas piston is too stiff, and the gas block is off center, this can cause binding.

briansmithwins
November 25, 2008, 03:54 PM
The AK manual I have says:

http://i2.photobucket.com/albums/y3/briansmithwins/AKgaspistonplaypage102.jpg

Full .pdf of the English translation of the Sov manual is here; http://www.box.net/shared/cu2djae1zb

For what it's worth, my Arsenal SLR107FR has a loose piston and has never had any problems. I personally think the condition of your crown and the quality of your ammo is going to have a little more effect on accuracy than the tightness or your gas piston. BSW

expvideo
November 25, 2008, 03:56 PM
The gas piston doesn't contact the barrel.

All the function of the gas piston is taken care of entirely inside the gas block. The gas tube is just there to guide the gas piston into the gas block.

If the gas piston is too stiff, and the gas block is off center, this can cause binding.
+1
And since the gas block is usually slightly off center due to the loose tolerances that are typical of AKs, this can very easily be an issue. Especially in a Romanian AK, which are notorious for canted gas blocks.

elmerfudd
November 25, 2008, 04:00 PM
It contacts both the gas block and the gas tube, which do contact the barrel. Having any slop in it means it can contact the gas block slightly differently with every shot and thus change the harmonics.

expvideo
November 25, 2008, 04:13 PM
It contacts both the gas block and the gas tube, which do contact the barrel. Having any slop in it means it can contact the gas block slightly differently with every shot and thus change the harmonics.
No. It would only contact the gas block upon returning to the forward position, in which case the bullet has long since left the barrel.

Hoppy590
November 25, 2008, 05:52 PM
clearances, not tolerances
Actually in the case of AKs it's both. But you're right. I meant clearances.

very true. clearances excuse loose tolerances

Thin Black Line
November 25, 2008, 10:27 PM
Some like them loose. Some like them tight. Some who like them loose are wound tight. Some who like them tight said it was ok to use them loose and don't want to beat a dead horse until their tight ones become loose.

MAKster
November 26, 2008, 09:59 AM
The piston and bolt carrier on my MAK-90 are tight with no wiggle at all.

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