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Discussion Starter #1
Two initial pieces of info: I'm NOT going into Vendor names right now... I'm trying to contact a vendor as I post - following data may very well be a one of. Second - the vendor isn't ORF: no need to worry about their pistons :)

I had occasion to hit the range today with my TGI VZ58. I had recently installed a US piston into it. Fired 50 rounds of Golden Tiger, and all was going well.

On a last shot bolt hold open, I noticet the gas piston tail still sticking out. Thought I had a broken spring? Nope - had this:





IF YOU HAVE RECENTLY PURCHASED A US VZ GAS PISTON... keep an eye on it. CHECK it for battering. Again, THIS IS NOT FROM ORF... and I don't want to go into sources until I've had a chance to let the manufacturer comment. Soon as we can connect? I'll update this thread.

This should NOT be a safety issue: Worst thing I experienced was a temporarily inoperative rifle... and a little trouble getting the piston out. I'm only posting this data "early" as a caution for something that MIGHT, if left to itself, cause some damage to a VZs gas piston channel.
 

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Thought about buying a US piston...

I had though about buying a US piston... I'll hold off for a while... Thanks for the heads up!
 

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Re: Thought about buying a US piston...

Lethal_inj said:
I had though about buying a US piston... I'll hold off for a while... Thanks for the heads up!
As mentioned above, I believe this was a one-off mistake in the heat treat.

Don't let this put you off.
 

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Discussion Starter #7
I CAN add one item: The piston is Stainless (magnet no sticky). While stainless is fine for AKs, I'm questioning whether or not it is hard enough for a VZ... that piston end undergoes much more of a hammer effect.
 

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Trotsky said:
I CAN add one item: The piston is Stainless (magnet no sticky). While stainless is fine for AKs, I'm questioning whether or not it is hard enough for a VZ... that piston end undergoes much more of a hammer effect.
Shouldn't make a difference. FALs use the same type of piston action.
 

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Discussion Starter #11
Update - got with the Manufacturer. MY piston, and one other, seem to have been odd exceptions. Good news, as the problem is isolated, and not a general issue. He is kindly sending me a new one. As the ORF folks have said? Root cause seems to be a heat treating issue.
 

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Rapid Fire said:
Guys,
I would guess it had not been heat treated. The samples we ran in the proto we did not HT and it did the samething, still ran fine bent and all.

[email protected]
Same here. Both my ORF proto (non-HT) and Weaponeer piston bent within 300 rounds. Gun kept firing but it seems like there are some larger shock loads in the VZ not in the AK.
 

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If you compare the gas systems of the AK and the VZ, it should be obvious that there are points of greater stress in the Vz, notably where the rear of the piston and the front of the bolt carrier meet. In fact, every Vz I have seen shows some degereee of battering to the front face of the bolt carrier. This is why the rear of the piston is domed. It makes the end of the piston less apt to mushroom but it does peen the carrier as a consequence. None of this should create a problem in a properly built rifle. The SKS uses the same concept but the addition of a tappet probably does lessen the force exerted on the face of the carrier.
 

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Boy, reading that sure makes me sound like an arrogant prick!!!! I'm not....I swear. Sometimes I just get too friggin' technical.
 

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Thanks for the heads up Trotsky!
 

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Discussion Starter #16
You know? I confess - I'm still learning how the VZ works in comparison to an AK. I've built a LOT of 47's and '74's, and was amazed at the incredible difference in strength needed for a VZ piston in "hammer & anvil" mode, vs an AK in "push" mode. Working backwards? I wonder if this was a consideration that Kalashnikov had in using a gas piston fixed to the carrier...
 

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May well be. The AK setup is certainly more forgiving with respect to quality control. If you've ever owned a soviet built vehicle or complex mechanical device, you've learned ALL about Soviet quality control!! They were in a world all their own. :roll:
 

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In Communism, there is no competition, everything is government owned ...



Wilhelm said:
May well be. The AK setup is certainly more forgiving with respect to quality control. If you've ever owned a soviet built vehicle or complex mechanical device, you've learned ALL about Soviet quality control!! They were in a world all their own. :roll:
 

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Trotsky said:
Update - got with the Manufacturer. MY piston, and one other, seem to have been odd exceptions. Good news, as the problem is isolated, and not a general issue. He is kindly sending me a new one. As the ORF folks have said? Root cause seems to be a heat treating issue.
Isolated?

Heat treat is usually done in large batches. If there is one bad, then probably the whole lot is bad. Most small companies have to subcontract heat treating out as it is a specialized procedure.
 

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Hootbro said:
Isolated?

Heat treat is usually done in large batches. If there is one bad, then probably the whole lot is bad. Most small companies have to subcontract heat treating out as it is a specialized procedure.
Some of our forum craftsmen roll their pistons out on a lathe one at a time and heat treat in their shop as needed.
 
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