Author Topic: Yugo M59 SKS fires once, does not eject, bolt sticks  (Read 9460 times)

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thatmattguy

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Yugo M59 SKS fires once, does not eject, bolt sticks
« on: September 23, 2019, 09:52:20 PM »
Hey all, looking for some help with my virgin SKS I purchased a few years back.  Its a yugo M59 SKS.  When I load it with 1 round or more and fire it, it shoots great, but bolt sticks (only when I fire, when I just pull the bolt back and forth it moves fine), fails to eject, and to get it to eject the spent round I have to wait a while and it moves normal or bang the bolt hard to open the bolt.  What have I done to troubleshoot?  When I first got it I cleaned it to a stupid level of detail taking it down all the way to individual components in the trigger group. I also worked on the pin and firing pin so they moved in the bolt much better (it was getting stuck which I had read leads to slam firing).

What do I think?  Has to be one of the two pieces of the bolt or the chamber.  I really don't see how the gas system could cause the bolt to get temporarily stuck (And yes the knob on the gas block is down and to the right, not at the top).  I lean towards chamber but it looks alright to me. 

Anyone ever seen/dealt with this?  Any thoughts? 

Boris Badinov

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #1 on: September 24, 2019, 12:19:55 AM »
Can you clarify:

Does the bolt get stuck in rearward motion of recoil?

Or

Does it get stuck as it travels forward , failing to  return fully into battery?

Also:
Did your detailed  cleaning include removal and inspection of the piston extension and spring that are housed inside the RSB?
« Last Edit: September 24, 2019, 05:32:58 AM by Boris Badinov »
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Rocketvapor

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #2 on: September 24, 2019, 01:27:06 AM »
------ or bang the bolt hard to open the bolt. -------
When I first got it I cleaned it to a stupid level of detail taking it down all the way to individual components in the trigger group
Does it HAVE an Op-Rod (Piston Extension) now, after cleaning?

What do I think?  Has to be one of the two pieces of the bolt or the chamber.  I really don't see how the gas system could cause the bolt to get temporarily stuck .  I lean towards chamber but it looks alright to me. 
Stickage from low gas/leakage would be pretty common. 
I run No Gas Sometimes and it does take a little force to pull the bolt back. 
Especially after shooting cheap ammo. 

That said, a properly operating gas system should still blow the carrier back.

« Last Edit: September 24, 2019, 01:57:34 AM by Rocketvapor »
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GuitarmanNick

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #3 on: September 24, 2019, 03:58:51 PM »
Does your SKS have matching numbers on the bolt and receiver?

If you have the gas turned down too low, the bolt will not open after firing.

Are you also saying that the bolt sticks in the closed position and must be forced open to extract the fired shell casing?

thatmattguy

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #4 on: September 27, 2019, 08:59:27 AM »
Sorry, been a rough week at work so just getting time now to come back and post.  To answer the questions
The bolt sticks forward, never goes back.

Op-Rod is there an was pulled and cleaned/lubed, put back, I will say this sucker is very hard to put back in as the spring has little give, maybe thats the issue?  I have tried cheap (steel casing/steel core) and not so cheap ammo (brass, copper coated lead), no difference.

Not sure about matching numbers, honestly never checked.  Came as a virgin unfired rifle from a trusted vendor, but I will check.  Also you mention if I have the gas turned down too low.  I can adjust that?  And yes after firing I really have to hit the bolt handle pretty hard in order to get it to go back and eject the spent shell casing.  Sometimes I have to wait a bit at which point it moves like normal.

Thanks guys.

Boris Badinov

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #5 on: September 27, 2019, 09:18:15 AM »
^^^This sounds like you've got a significant gas leak or blockage somewhere.


Your rifle is an not an M59. It's an M59/66
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GuitarmanNick

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #6 on: September 27, 2019, 12:09:01 PM »
The fact that the bolt is hard to open after firing makes me suspect the chamber is contributing to the problem you are experiencing.

When the round is fired, the case will expand in the chamber. If there is crud on the chamber walls, it can stick and be very difficult to open.

Take the rifle apart and clean the chamber with the proper brush until it shines! Likely yours has varnish deposits from not being properly cleaned after shooting steel cased ammunition.

Disassemble the gas valve and clean the port in the barrel, all valve parts, and reassemble. Inspect the piston and gas tube and insure they are clean and move freely. This would be a good time to check the fit between the outside of the piston and inside of the tube wall. A large gap here will keep the rifle from cycling properly. If the parts bind, the rifle will also have problems cycling.

To reinstall the operating rod, it is easier if you use a punch to push the operating rod and compress the spring with one hand while closing the retainer with the other. It needs to be fairly stiff, but should move freely in the housing without the spring installed. This is another area where clearance is important, but a large gap could create problems.

In most cases, proper cleaning and lubrication is all that is needed to make an SKS run reliably.

The Yugos sometimes have issues with the gas valve, which is adjustable and can become blocked.


bobbers

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #7 on: October 03, 2019, 07:29:02 PM »
What position is the gas valve in?  The one that regulates single shot vs. semi-auto?  And given that extra valving is it thoroughly clean?  Not the rod, not the tube, the valve itself.
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Boris Badinov

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #8 on: October 03, 2019, 07:55:25 PM »
The fact that the bolt is hard to open after firing makes me suspect the chamber is contributing to the problem you are experiencing.

When the round is fired, the case will expand in the chamber. If there is crud on the chamber walls, it can stick and be very difficult to open.

Case expansion, even in the dirtiest chamber, won't create enough resistance to counter the force of the fully gassed/functional op-rod.  If the chamber is crudded up enough, the extractor claw will release from the stuck casing. But a fully gassed op-rod will still send the bolt and carrier rearward into recoil regardless. (Wouldn't it?)

If the bolt and carrier don't recoil when firing -- then it still seems like under-gassing (blockage or leak) is the most likely issue.






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GuitarmanNick

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #9 on: October 04, 2019, 10:02:19 AM »
I have seen quite a few ARs that must be mortared to open the bolt after firing steel cased ammo and not being cleaned properly. I would think it could contribute to a sticky bolt in any rifle that depends on gas to cycle. My thinking is that even though the systems are of different designs, the physics and operation are essentially the same, indicating some potential problems may be shared.

I agree that the main issue appears to be an obstruction or missing, dirty or damaged part somewhere in the gas system.

Boris Badinov

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #10 on: October 04, 2019, 10:07:41 AM »
Is there an O-ring, or some other type of seal on the 59/66 gas block?

I seem to recall having watched a DIY repair video that involved a makeshift replacement seal for the 59/66.
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Dannyboy53

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #11 on: October 04, 2019, 08:07:12 PM »
There are no "o" rings in the gas system, at least there are none in my 59/66A1. thatmattguy if you have detailed the entire gas system I would look at the chamber next...again! I had the same thing happen to my old /26\ 3 million gun. Turns out the chamber was gummed up with that crap the ammo manufacturers used to coat the older rounds with. I put a brush in a section of cleaning rod, chucked up on it with my drill and scrubbed it out with bore cleaner. I never had that problem again. GuitarmanNick gave some sound advice.

I don't know if that is your problem but it may be worth trying!
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thatmattguy

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #12 on: October 06, 2019, 07:27:21 AM »
Thanks for all the replied.  I just got back from a work trip so I should have some time tomorrow to go at it.  I cleaned the gas system with the exception of the gas block attached to the barrel (which is set for semi, not single which means it set down and towards the right) as I did not see a way to do as such.  I can use some compressed air and make sure it flows.  I have no o-rings and I have not seen that mentioned.  The piston flows free in the tube, maybe too free?  Not sure what the dimensions should be but I have a fairly decent caliper if someone could relay specs.

Very well could be the chamber, not checked that in some time, I really need to spend some time really going to town on that.

I will post back after I get those two tasks done.


Boris Badinov

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #13 on: October 06, 2019, 07:43:39 AM »
The piston flows free in the tube, maybe too free?  Not sure what the dimensions should be but I have a fairly decent caliper if someone could relay specs.

There is a very simple way to test piston fit:

1) Remove gas tube with piston in place.
2) Hold the tube horizontally and seal the tube entirely by covering it with the pad of your thumb.
3) Now turn the tube 90degrees to the a vertical position with your thumb still covering the opening

If the piston fit is correct, it will fall very slowly by gravity. You will be able to feel the suction resistance on the pad of your thumb as the piston falls.

https://www.youtube.com/watch?v=Ba7Foczx-U4

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Boris Badinov

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Re: Yugo M59 SKS fires once, does not eject, bolt sticks
« Reply #14 on: October 06, 2019, 07:50:36 AM »
It's often easy to miss dried up crud that obstructs the gas port.

This is a cut-away photo of and AK but the concept is the same to test for and clear any obstructions from the port:



In an unobstructed port, the port cleaning tool should go into the barrel with little to no resistance
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