Just got my SKS. Important gas piston question.

[xxxleafybugxxx]

I just recieved my sks and got it cleaned from all the cosmoline.
Only question I need answered before I Go and shoot it this... is the gas piston supposed to move freely inside the gas tube? When I insert the piston into the tube it does require a bit of force to make it go through.. Does this present a safety hazzard, or will shooting it make it do what it needs to do?
I lube it pretty good but that didn't seem to make a difference.

 

[Sam1911]

Well....hmmm....mine doesn't require any force at all to move through its normal range of motion, though I recall it does get a little stuck if you push it all the way to the rear when disassembled.

Shouldn't be any danger -- the worst case will be that it doesn't cycle properly. (Remember that certain versions of the SKS have an "off" switch for the gas system, making it a manual repeater.)

But if that doesn't work right, what else isn't right? You've detail stripped and cleaned everything? No rust? No visible damage? All the cosmo out of the bolt? (!!!!!)

 

[xxxleafybugxxx]

There are some minor areas of surface rust... nothing that scares me.. like some on the mag, some on the exterior of the reciever.. nothing bad.. but all of the cosmo is out of the important areas.. the firing pin moves back and forth when i shake it everything seems fine. The best part is a super shiney bore.
Only area of concern for me is the piston region. The lever that locks that in is very very tough to move. And under the bottom of the gas tube there is some corrosion.

 

[Mauserguy]

It should fit tight, and may have some resistance, Also, as a tight fit, it may move easier in one position than in another position and will tend to bind if pushed down to the narrowing area. This is normal. Having said that, you should clean the interior of the gas tube well as they are subject to rusting. Scrub well.
Mauserguy

 

[49willys]

I wouldnt think lubricating the gas piston would do any good.Wouldn`t any lube get burned off by the hot gasses within a few rounds?I would also think a little resistance would be better than slop,less blow by.I could be wrong,just a thought.

 

[xxxleafybugxxx]

ok so this sounds normal?
I'll go shoot it then.

 

[Mauserguy]

Don't just shoot it; take pictures and report back on it. Is this a chinese SKS?
Mauserguy

 

[xxxleafybugxxx]

Here are some pictures of the gas tube and piston.
the first picture is to show that holding the gas tub up the piston doesn't fall all the way down by istelf. Its tight in there.

the other pictures are showing the tube with light shining through. They are a little dirty, but i shot air through it and tried running some rags.. maybe i just don't know how to propberly clean it?

And the other picture is of the bottom of the gas tube. I don't think that that stuff is rust because the actual metal doesn't look compromised. Maybe its dirt??
However none of the rust is serious.
For being a chinese surplus I believe its in decent shape.

 

[trueg50]

Does the piston move freely in the tube? Judging by the looks of it, the last owner wasn't the most diligent in cleaning after corrosive ammo.

After shooting carbon builds up around the tip and rings of the piston, so my piston won't easily fall out past 1/4" of the tube. I have to shake it like you're getting the last bit of ketchup to flow to the nozzle.

Thorough cleaning of the piston rings, and the last 1/4" of tube should fix the issue.

 

[Cee Zee]

the last owner wasn't the most diligent in cleaning after corrosive ammo

I shot thousands of rounds of corrosive ammo through my Norinco before I was ever able to get the gas tube apart. It didn't look anything like this one does. My guess would be improper storage (foam case or something similar maybe). I don't know really. Maybe water managed to get in there some way.

 

[Mauserguy]

Yeah, that's rust, and the inside of the gas tube is rust etched. With a good cleaning, though, it should be fine. When I got my Chinese SKS, I had to beat the piston out with a hammer and punch. It ran 100% after that.
Mauserguy

 

[Sam1911]

This is what I'd do: Get a slotted cleaning rod tip for shotguns (they're bigger) and some steel wool. Put the cleaning rod tip in a short section of rod and chuck that into a cordless drill. Tear off a section of wool and stick it through the slotted tip. Put some Hoppes or other oil on the wool, and then run that drill at medium speed while you massage that steel wool "swab" back and forth inside the gas tube. You might even be able to do the same thing on a small scale (like with a .22 tip) inside the smaller diameter section.

That should knock down the rust enough that the piston will be able to slide freely.

This is a significant difference between the SKS and AK. The AK's piston rattles around inside what is essentially just a guide channel. The tube doesn't form any kind of a seal at all (it's crimped in a star pattern, so only a few "points" touch the piston head), except right at the gas block. With the SKS, it's more like a normal piston and fits fairly tight.

You don't usually hear of unreliability issues caused by this, but they can happen.

 

[Water Garden]

mine does not offer resistance... sounds like there is crud built up in there.

 

[Miked7762]

That's not rust, it's dried and oxidized cosmoline that wasn't cleaned out. Use a non-evaporating solvent (kerosene, WD-40, etc.) and a stiff bottle brush or a nylon .45 bore brush to really get in there and scrub it out. Very hot water will help break apart the larger chunks.

 

[Sam1911]

Milked certainly could be right. The method I suggested is the usual treatment for such gunk stuck in Mosin chambers, causing hard extraction.