AK stuff: gas piston is dragging on the gas tube and not bonding with the gas vent

[ucla_jtsuei]

Pretty much what the title says. I think my piston is angled slightly off, causing it to fail to mate properly with the gas vent.

When i attach the gas tube, the tube can successfully guide the piston into the vent, but there is a great deal of drag. If I release the bolt carrier about 0.5 inches from "in-battery" position, there is enough drag to stop the piston/bolt carrier from sliding into battery. Releasing the bolt carrier any further back gives me enough spring tension to slam it home.

Here are some pictures of the problem:







Without the gas tube on, the only way to mate the piston with the gas vent is to apply upward force to the piston. Trouble is, that upward force causes the bolt carrier further back to drag on the rails - and I think that's what is ultimately preventing the carrier from sliding smoothly.





With the gas tube on, the tube provides the "upwards force" that my left hand simulates in the picture. Trouble is, the bolt carrier is still dragging on the receiver rails.



Any fixes? (already tried whacking the piston to bend it, but no success)

[crob241]

ak

Is the recvr. a bent flat or commercial like Nodak? The rails guide the bolt carrier if they are not straight or too tight could be a problem, also is the timing correct when the bolt goes in battery, is it headspaced right? Is the brl., sight posts and gas port original or been replaced, is the gas tube the correct one, ie ak47 or ak74. I would give it a good visual inspection before using a hammer.

[ucla_jtsuei]

The receiver is a bent flat. I don't think it's the rails: I tried a couple of other bolt carriers, and they had no problems. Headspace isn't an issue: I've already shot 200+ rounds through it. FSB, RSB, gas tube, and gas port are all original.

[HotRails]

The receiver is a bent flat. I don't think it's the rails: I tried a couple of other bolt carriers, and they had no problems. Headspace isn't an issue: I've already shot 200+ rounds through it. FSB, RSB, gas tube, and gas port are all original.

WHen you say that you tried a couple other bolt carriers, you mean you didn't have this problem with them right? Did you change your gas piston? Go over it one more time to make sure there are no burs on the upper and lower rails up front. Is it possible lower rails are misaligned causing a pinch?

[ar15barrels]

The receiver is a bent flat. I don't think it's the rails: I tried a couple of other bolt carriers, and they had no problems.

So you already KNOW the solution.

What was the question again?

[thedrickel]

I don't understand the problem. When you pull the trigger, does it go bang? And then go bang again when you pull the trigger again?

[Faust]

Did you swap-in complete piston+carrier? or was it just the carrier with the same piston all the time?
Is there wobble between the piston and bolt carrier?

[ar15barrels]

I don't understand the problem.

It rubs.
He does not like that it rubs.
It does not matter to him that rubbing is not a problem.

I'm wondering if he has removed the hammer from the reciever to check if it still rubs without the hammer...

[HotRails]

It rubs.
He does not like that it rubs.
It does not matter to him that rubbing is not a problem.

I'm wondering if he has removed the hammer from the reciever to check if it still rubs without the hammer...

Wait, my understanding was that the BC was not closing all the way due to the friction or misalignment of the gas piston? If it is just a little friction and is still functioning then just take a file to the rails until there is a smooth action.

[ar15barrels]

Wait, my understanding was that the BC was not closing all the way due to the friction or misalignment of the gas piston?

Headspace isn't an issue: I've already shot 200+ rounds through it. FSB, RSB, gas tube, and gas port are all original.

I'm guessing the bolt closes ok.

[uxo2]

Put the gas tube back on and asssemble it .
Pull charging handle back and release.

DO NOT RIDE IT>>>>Let it go foward under nornal spring power.

If it goes foward ...Go and SHOOT IT...Its an AK..Not an AR


Does it hang up ??

let us know

[M. Sage]

^^ Exactly.

To the OP: The gas tube on an AK isn't entirely a gas tube. I'd say that 80% of the reason it's there is to guide the piston back home into the gas block. Look down the tube and you'll see that it's designed to vent gas around the piston. Most (all?) of the work is done while the piston is in the gas block.

I'd look closer at the rails than the gas piston, personally. The piston should have a bit of play in the carrier, every AK I've disassembled has. How much force does it take to align the piston with the gas block, anyway? Tried "bending" it up a little?

[ucla_jtsuei]

DO NOT RIDE IT>>>>Let it go foward under nornal spring power.

I thought I made it clear I know how AKs are supposed to charge - ya know, with my discussion of there apparently being enough spring recoil tension to force the piston in from x>0.5" away from in battery.

I'd look closer at the rails than the gas piston, personally. The piston should have a bit of play in the carrier, every AK I've disassembled has. How much force does it take to align the piston with the gas block, anyway? Tried "bending" it up a little?

The piston definitely has a lot of play - more than most of the AK's I've handled. The piston is actually a little loose, too. But the play isn't loose to the extent that it can slide into the gas block with a gentle upward push. I pretty much have to get some leverage with my hand and push the piston upward (maybe 10-15 pounds of force) to get it in. I basically am "bending" it to get it to slide in.

It rubs.
He does not like that it rubs.
It does not matter to him that rubbing is not a problem. (obviously, the possibility, however small, of having an out-of-battery discharge is not a "problem")

I'm wondering if he has removed the hammer from the reciever to check if it still rubs without the hammer...(yes)

Got anything useful to add, big guy?

[HotRails]

Ok so lets clarify:
When the gas tube is in, is this sufficient to guide the gas piston into the gas block properly?
Did you change your gas piston to comply with 922r? If so, maybe it is not machined well/ not installed properly
You also mentioned that there was friction when the BCG was further back on the rails. Where is the contact that is causing the friction?
Is it possible that:
1) There are burs on rails/BCG?
2) You did not file down the ejector tip quite enough and the bolt is getting hung up there, ever so slightly?
3) The bottom rails are not properly aligned, causing a pinch that retards teh BCGs forward movement?

[oaklander]

My sense is that something needs to be hit with a hammer somewhere. Either the rails, or the gas port.