Author Topic: Misfire Troubleshooting  (Read 12110 times)

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Boris Badinov

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Re: Misfire Troubleshooting
« Reply #15 on: August 15, 2019, 07:12:31 PM »
Is the bolt Chinese?
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Andronicus

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Re: Misfire Troubleshooting
« Reply #16 on: August 15, 2019, 07:59:01 PM »
Is the bolt Chinese?
I bought it as a "Chinese" sks from Cabela's Canada. I believe that all the parts are Chinese.
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Andronicus

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Re: Misfire Troubleshooting
« Reply #17 on: August 15, 2019, 08:08:42 PM »
The area of your Bolt than engages the Locking Shoulder looks a little larger than normal but could just be the photo. And is that rough file markings on that surface?
On closer inspection, it does look like file marks on the bolt (that 45° portion on the lower rear).
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murray

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Re: Misfire Troubleshooting
« Reply #18 on: August 16, 2019, 10:06:46 AM »
That's what engages the Locking Shoulder in the receiver and sets head space. If primers are backed out of any empties beyond the back surface of the case itself, that would be a sign of excessive head space. I'd try to find someone with gauges and check it to be sure.
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Rocketvapor

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Re: Misfire Troubleshooting
« Reply #19 on: August 16, 2019, 11:05:55 AM »
Those marks could be 'as machined'.
The worn area in the center is where the shoulder hits. 
It appears to be lower than the 'file' marks.
+1 on a head space check. 

I would also do a black marker check of the bolt surface, shoulder, rear of the firing pin, hammer. 
Well I guess my new **** stirrin paddle don't work . I got a like . WTF 😈

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Andronicus

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Re: Misfire Troubleshooting
« Reply #20 on: August 16, 2019, 04:45:54 PM »
That's what engages the Locking Shoulder in the receiver and sets head space. If primers are backed out of any empties beyond the back surface of the case itself, that would be a sign of excessive head space. I'd try to find someone with gauges and check it to be sure.
Will I need to find a gunsmith to do the gauge test?

I did try moving the bolt when in battery position.  By sticking my finger through the open magazine, I was able to move the bolt about 1/2 mm with no round in the chamber.  With a round in the chamber there was no visible movement, but it must have moved slightly because I could hear the clicking of the movement.  Obviously this is not a precision test, but does it tell you anything useful?
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Andronicus

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Re: Misfire Troubleshooting
« Reply #21 on: August 16, 2019, 04:49:47 PM »
Those marks could be 'as machined'.
The worn area in the center is where the shoulder hits. 
It appears to be lower than the 'file' marks.
+1 on a head space check. 

I would also do a black marker check of the bolt surface, shoulder, rear of the firing pin, hammer.
Tell me more about this black marker check?  I was able to observe a lot of the workings by operating the various components while others were removed.  I (an untrained newb) couldn't see anything that looked 'off'.

I am confused why it works great after cleaning, but starts acting up after 50 or 80 rounds?  And each time it seems to be a different symptom.
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murray

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Re: Misfire Troubleshooting
« Reply #22 on: August 16, 2019, 05:21:39 PM »
That's what engages the Locking Shoulder in the receiver and sets head space. If primers are backed out of any empties beyond the back surface of the case itself, that would be a sign of excessive head space. I'd try to find someone with gauges and check it to be sure.
Will I need to find a gunsmith to do the gauge test?

I did try moving the bolt when in battery position.  By sticking my finger through the open magazine, I was able to move the bolt about 1/2 mm with no round in the chamber.  With a round in the chamber there was no visible movement, but it must have moved slightly because I could hear the clicking of the movement.  Obviously this is not a precision test, but does it tell you anything useful?

If you're anywhere near Mission BC then Hical.ca could likely help, and the average SKS owner is not going to have gauges, so finding a 'Smith around you with 7.62X39 gauges may be in order.

You'll need the precision gauges to know for sure but what you describe sounds fishy. "Seeing" something move .005" is difficult at best, and there should be some movement of a cartridge in the chamber, but very little, and that's why gauges are so important. Is it the right amount or too much?


https://murraysguns.com/shop/

If you feed it junk ammo, why should you expect filet mignon results? Well now you can, with our new "Neck & Throat" chamber reaming service!

Boris Badinov

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Re: Misfire Troubleshooting
« Reply #23 on: August 16, 2019, 05:24:15 PM »
Can you post a photo of the serial number on the bolt?

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Andronicus

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Re: Misfire Troubleshooting
« Reply #24 on: August 16, 2019, 06:32:38 PM »
That's what engages the Locking Shoulder in the receiver and sets head space. If primers are backed out of any empties beyond the back surface of the case itself, that would be a sign of excessive head space. I'd try to find someone with gauges and check it to be sure.
Will I need to find a gunsmith to do the gauge test?

I did try moving the bolt when in battery position.  By sticking my finger through the open magazine, I was able to move the bolt about 1/2 mm with no round in the chamber.  With a round in the chamber there was no visible movement, but it must have moved slightly because I could hear the clicking of the movement.  Obviously this is not a precision test, but does it tell you anything useful?

If you're anywhere near Mission BC then Hical.ca could likely help, and the average SKS owner is not going to have gauges, so finding a 'Smith around you with 7.62X39 gauges may be in order.

You'll need the precision gauges to know for sure but what you describe sounds fishy. "Seeing" something move .005" is difficult at best, and there should be some movement of a cartridge in the chamber, but very little, and that's why gauges are so important. Is it the right amount or too much?
Mission BC is about 12h drive from here.  I'm checking with some local gunsmiths.  If that fails, I found a Canadian shop that will rent one for $20 plus shipping (True North Arms).
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Rocketvapor

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Re: Misfire Troubleshooting
« Reply #25 on: August 16, 2019, 07:13:02 PM »
A gunsmith familiar with the SKS is the best path. 

Looking at the picture of that pin it looks like at least a few times during the gun's history, the hammer followed and jammed the pin.  I would black marker it and the hammer face to see if it is happening again.  (Red arrows in pic)
When it misfires, you can pull the trigger and hear the hammer fall?

The shoulder/ bolt contact surface can be blackened to see where the edge hits. (Blue arrows)

Tight headspace can cause action issues.  I doubt it's excessive headspace. 
You can check headspace with shim stock.  Use your normal malfunctioning ammo.  It would be best to use dummy rounds but at least pull the pin and ease the bolt into battery.  Then remove the cover and recoil spring.  Push forward on the carrier and check with shim stock.  Even with the pin pulled, a live round in the chamber you need to observe loaded gun protocol.  There is nothing to hold the bolt/carrier if the round fires. 

The rear surface of the carrier (Green arrows) seems to be contacting the rear of the receiver.
That could be a sign of a weak recoil spring.

The gas system may be a problem but if the action picks up a round, goes into battery it should fire. 


 
Well I guess my new **** stirrin paddle don't work . I got a like . WTF 😈

Flo just received her EXPERT Mid range card from the NRA.

https://www.yahoo.com/news/famed-ex-uss-john-f-003916449.html

Andronicus

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Re: Misfire Troubleshooting
« Reply #26 on: August 16, 2019, 08:18:34 PM »
Can you post a photo of the serial number on the bolt?
1069
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lonewolf

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Re: Misfire Troubleshooting
« Reply #27 on: August 16, 2019, 08:51:38 PM »
Also check a make sure your gas port hole is not partially plugged.

murray

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Re: Misfire Troubleshooting
« Reply #28 on: August 20, 2019, 10:28:06 AM »
If you haven't rented yet, Brownells sells the No Go Gauge for $29 + shppg of course, (and they can likely be found cheaper) and the No Go is the only gauge you really need. You can add a couple of layers of scotch tape the the back of the gauge to use as a "Field" gauge, and that should cover all bases.

Those numbers look suspicious to me. Don't think they are original. And if I understand correctly, 1069 are not the last 4 digits of the serial number on the left side of the receiver. Correct?
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If you feed it junk ammo, why should you expect filet mignon results? Well now you can, with our new "Neck & Throat" chamber reaming service!

Andronicus

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Re: Misfire Troubleshooting
« Reply #29 on: August 23, 2019, 02:02:49 PM »
If you haven't rented yet, Brownells sells the No Go Gauge for $29 + shppg of course, (and they can likely be found cheaper) and the No Go is the only gauge you really need. You can add a couple of layers of scotch tape the the back of the gauge to use as a "Field" gauge, and that should cover all bases.

Those numbers look suspicious to me. Don't think they are original. And if I understand correctly, 1069 are not the last 4 digits of the serial number on the left side of the receiver. Correct?
Serial numbers:  you are correct that 1069 is not the last four digits of the receiver sn.  None of my parts have numbers that match.

Rocketvapor suggested that
Quote
Tight headspace can cause action issues.  I doubt it's excessive headspace.
If this is the case, wouldn't the "go" gauge be the correct one to measure too tight headspace?  Or are you suspecting too loose headspace?

ps the cost of a local gunsmith was going to be over 30% of a 'new' sks (not including any corrective modifications), so I don't think I can justify that.

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