Gas Leak, bad ejector, or soemthing else?

[mccdave]

I have a new to me SKS (Chinese I think, but trying to identify).  Every time (in 30-50 rounds) I shoot it the empty brass is removed from the chamber, but jams before the next round is loaded into the chamber.  The next round is moved towards the chamber, but the bolt does not close all the way because the last round is still there.  99% of the time the empty brass sits longways between the bolt and barrel but once it is more of a stovepipe situation (explained futher below). 

?   I have fully taken the rifle apart and cleaned it.  I have specifically cleaned the gas port in the barrel, and it seems to flow air (gas) fine.
?   I have checked the "seal" around the gas piston and tube simply by blowing in the end of it (with the assembly off the gun) and validating there is strong pressure (very little air leak). 
?   The piston moves freely in the tube come out the end about an inch. 
?   The piston extension moves freely and extends about 3/4"-1" when fully depressed.  I have plugged the chamber and applied air pressure to the end of the barrel.  I get some air leakage between the gas block (housing around the gas port in the barrel) and the piston tube.  I don't know how much leakage is "normal". 
?   I have done an experiment with wrapping a couple wraps of thread tape around the gas block before the gas piston/tube is installed to try to get a better seal.  When shot it blows all the tape off and the same result with the spent brass. When I did this it stove piped the round making me think the gas leak could be the problem as it was "closer" to cycling.
?   I have tried different loads (igman, PMC bronze, and 1 other but don't remember the brand), exact same results
?   When I load multiple rounds into the magazine and manually cycle the bolt the shell is extracted from the chamber, ejected from the gun, and the next round loaded without issue.

Any suggestions on "seal" the gas leak or maybe a little bit of leakage is expected as there is no real "seal" just a metal to metal fit.  Could the extractor be the problem?  Open to ideas and tests I could do to trouble shoot more.

Thanks in advance for any help.

[PAX]

Welcome aboard m from Kai. Note of caution: Be very careful when handling your weapon in that condition. The hammer can still fall, if the trigger has been pulled, when the round is out of battery, then the bolt is closed, if there's bad sear engagement. PAX

[Greatguns]

It's not an M59/66 Yugo is it? Gas system shut off valve and all that?? First thing to check on an M59/66 is the gas valve and port.

Assuming it is a standard SKS and not the M59/66, first thing to check is to make sure the recoil spring assembly is in the correct way. Squiggly end goes into the bolt carrier. Second, double check your gas port and clean it out of any carbon build up restricting the hole (drill bit or gas port tool). Passing air through the port does not mean it is fully open. Carbon restriction will still allow air to pass, but not enough gas to allow for proper function.
Third clean the chamber with a bore brush to make sure it doesn't have any lacquer build up that is causing the casings to hang up in the chamber. Discharge of the cartridge causes the casing to expand and gives a different situation that you won't get when cycling the cartridges by hand without firing the weapon.
On the gas block to gas tube leakage, that can be an issue if the tube is too loose around the block. If you find there is excessive side to side movement at the front of the tube where it mates up to the  block you may need a replacement tube. If you have another SKS swap the tubes to see if that helps.

As to the extractor, check your casings to see if the rim is marked/damaged from the extractor rolling over it. This could be from the casing sticking in the chamber or a bad extractor.

[mccdave]

There is no gas shut off valve.  The gas block has a sling connection on it and nothing else.  When assembled, I can see slight movement side to side between the gas block and the piston tube when I move the piston tube.  1/16 of an inch or less.

[Greatguns]

Yeah, that seems a little much. Do you have another SKS to swap the tubes on to see if it is tighter and solves the problem?

[mccdave]

This is my only SKS so no spare parts (currently). 

[Greatguns]

Okay, if you can go through the double check on the areas/parts I mentioned, if it all checks out okay then try wrapping a thin strip of electrical tape around the gas block where the gas tube overlaps it. Use one or two layers as needed to cause the tube to fit tight and try a few rounds to see if it then works correctly. If it does then try a different gas tube that fits tight at the block. If that works then you are done. Otherwise, you may need to do something with the gas block itself.

Pics of the various parts and action may help to further identify your SKS and get the issue resolved

[PAX]

Don't worry, soon you'll have a collection of bits & pieces, PAX

[mccdave]

Status update:

* Shot the gun a little more, out of 10 rounds at least 8 just left the empty brass in the chamber, could manually cycle without a problem
* Disassembled the gun and cleaned, focused on the chamber, used a brush, solvent, it is clean, but not perfectly smooth (not a new gun and no history) - no change
* Used a drill bit (not in a drill) to further clean out the gas port in the barrel (through the gas block) - no change
* Verified Recoil spring installed with the squiggly end towards the front of the gun - towards the bolt carrier - no change
* checked cases no damage from the extractor

Final try:
* decided to try to thin layer of electrical tape on the gas block where the piston tube slides over.  after that the tube was a tight fit.

Shot 1 round - did not cycle, but this time the brass case was very stuck in the chamber (I mean very stuck).  Used a cleaning rod down the barrel to try to get it out.  Took some tapping and the primmer end of the brass case broke off from the rest of the case. 

I have seen some videos of using some cerrosafe to remove stuck cases, going to try that once I find some.  I have also ordered a new NCStar gas tube to see if that will make any difference - assuming the case will eventually come out.

[Greatguns]

Hmmmm, interesting. Once you get the casing removed try using a .410ga brass bore brush on a portion of a brass cleaning rod then stick it in a drill and run it back and forth. This will act to hone out the chamber to hopefully smooth it out without affecting the dimensions of the chamber.
Do you have any steel cased ammo to shoot through it or just the brass cased stuff? If you have steel cased, once cleaned out again try that first to see how it does.

Good luck with the NCStar tube, they have been known to be out of spec and of poor quality.

[murray]

I'd bet the NCStar tube as well. Pull the Gas Tube/Hand Guard off the gun with Piston, then turn piston around and see how tight/loose it may fit the large inside diameter of that tube. Bet it slops around significantly when it's supposed to be a very close slip fit.

When normally assembled for shooting, the Gas Tube is pushed forward by the Piston Extension Spring. See if you can grab the tube and pull it rearward against that spring pressure. If it moves rearward a noticeable amount, that may be a problem too. But welding a spot on the Gas Tube/Ferule area, and then removing appropriate amount of weld until the Latch holds it tight, will take care of that issue.