MODIFIED SKS RIFLES > SKS Troubleshooting

Sks Misfires

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Whitedice:

--- Quote from: Toad on March 11, 2013, 09:38:29 PM ---Seeing as it has been fired in cosmoline, have you cleaned out the gas system?

--- End quote ---
Yep. :)

Rocketvapor:
There are some videos on SKS functions, I tried to make one tonight but lighting didn't cooperate.
There seems to be a communication problem with questions and answers in this thread.
Could you answer these:

With the Trigger Group removed (put safety on to remove),
cock the hammer and push down on the disconnector.
Was it free to move, and the hammer stays caught on the sear ?
Try it a few times to make sure the cocked hammer doesn't touch the disconnector.

With fingers on either side of the disconnector, line up the Trigger Bar with the Sear and drop the hammer.
Did it go WHAP !!  ?

Looking into the bottom of the rifle action, cycle the bolt and watch the bolt "drop down".
Move the bolt slightly in and out of battery and watch the bolt drop then lift.
Does the bolt drop into battery?

Shine a flashlight into the action and find the firing pin.
Take a pencil, or screwdriver and press on the back of the firing pin.
Can you move it?

With safety on, hammer cocked, put the Trigger group back into the rifle.
Turn safety to fire, pull the trigger (make sure there is no round in the chamber)
and listen for the loud Whap !! of the hammer.
Does the hammer drop each time you cycle the bolt and pull the trigger ?

Take a FIRED CASE with NO BULLET and manually chamber it, drop the bolt.
Pull the trigger.  Does the hammer go WHAP !! each and every time ?


Don't play with live rounds unless you are someplace you can safely fire the weapon.

With about 1/16 inch of firing pin travel it is unlikely that the pin will not hit the primer, even with a deep set primer. 
Something around 0.015" is deep set.  Might not be all that reliable but it will dent the primer if the bolt drops into battery and the hammer WHAPs the pin. 
Add up excessive headspace (maybe 0.008"), a deep set primer (maybe 0.015"), a volcano ridge on the bolt face (about 0.004") and you still have a dented primer.


jbanzai:
Is there cosmo in the trigger group?  Did you clean the trigger group aggressively and not oil the friction points generously after?  These may be long shots, but both have caused major FTF's in my first SKS. 

BillyBang:

--- Quote from: Whitedice on March 11, 2013, 09:35:01 PM ---You mentioned the bolt may not be able to drop down far enough. How could I tell if this was the problem? would it be a visual thing, if so, what exactly should I look for.

--- End quote ---

That's what we're trying to figure out and to be quite honest,
you haven't been too lavish with the information about your rifle and it's condition.

What I alluded to, in my previous post was,
whether or not you had an all matching numbers rifle, especially the bolt.
Does the bolt number match the rest of the rifle?

Does the hammer drop when you pull the trigger (even at the times that the misfires occur)?
Or does the trigger act mushy with no hammer drop?
You see, a misfire is when the hammer drops, the FP hits home and there's no ignition.
So we need to use the correct terminology when explaining the problem.
You might be having a "Failure To Fire" (FTF) which could be caused by mechanical problems.

You also weren't very clear on whether or not you gave the entire rifle
a thorough cleaning including the trigger group and bolt.
Have you?
If you haven't,
then first thing, before you try anything else, I would completely strip the rifle and give it a thorough
cleaning as laid out in these instructions.
Then if the problems still exists, we've at least eliminated the chance that there is some
foreign matter interfering with the function of the mechanics of the rifle.
Once we have that established, we can go on to other reasons for the problem.








Whitedice:
BillyBang,
Sorry if I was not clear providing information. As I mentioned, Im not very familiar with these rifles yet so if I use the wrong terminology, feel free to correct me. As far as the cleaning the gun, I have completely stripped it down and cleaned it. Also, this gun is not a numbers matching rifle.

jbanzai,
There is not cosmoline in the trigger group, however, I may not have oiled the friction points well enough after cleaning. I have always tended to go light on the oil. I will oil it up a little more and see if this helps out at all. For oiling the trigger group, should I just use regular rem oil? This is what I did. But I saw some people putting some grease like or thicker oil on it if that makes any sense.

Rocketvapor,
 "cock the hammer and push down on the disconnector. Was it free to move, and the hammer stays caught on the sear ?"
     I removed the trigger assembly and the disconnecter moved when I pushed on it and the hammer remained cocked.

"With fingers on either side of the disconnector, line up the Trigger Bar with the Sear and drop the hammer.
Did it go WHAP !!  ?"
   I'm not entirely sure what you meant by this. So maybe I'm answering something you didn't ask. But with the trigger assembly back in place, I cycled the bolt back to cock the hammer and removed the receiver cover and recoil spring to watch. I pulled the trigger and the hammer did hit the firing pin with a whap.
   
Also, when I cycled the bolt it dropped into the battery. I think. With the bolt fully closed the rear of the bolt would drop about a little more than a 16th of an inch. So I think that would be it dropping into the battery.


To everyone, thanks for all of your help and suggestions. I will try oiling up the trigger group a little more, take it to the range again and see what happens. And hopefully this post made at least a little sense. I understand that I probably sound really dumb referring to all these parts and terms with 'that' so please bear with me as I learn. As far as I can tell, as I walk through all the suggestions proposed, everything works as it should. But this is an older rifle and maybe the parts are just getting worn and I will have to deal with and occasional MF or FTF whichever it is.
Thanks!

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