Pierced primers.

weasel1

weasel1

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Just wondering what you folks' take on this is.

First off, I have a Murray's firing pin installed in my SKS. I have fired 2 boxes of MFS soft points, 4 boxes of Norinco and about 2 boxes of Romanian surplus without issue until Monday. I ran about 4 boxes of Romanian. I had about 4 fail to fires. All 4 were light strikes and fired when rechambered. Yesterday I went to clean the rifle up and I find little primer bits in the bolt. The spring on the firing pin was also fried. I don't have the shells to confirm that the bits are in fact primer, but I'm 99% sure that's what they are. One other thing, before the pin was installed, I smoothed the bolt face and did a very slight chamfer in the fp hole to help prevent cookie cutting primers. I find it very hard to believe that my Murray's pin is to blame, but is it possible? The factory Russian pin is back in place for now, but I am slightly concerned. 80 rounds seems to be not very much to setting me on my way to slamfiring. Yes the rifle in question was quite clean before firing those 4 boxes. I am considering getting a neck and throat job (via Hical) done. Any thoughts or should I just run the free floating pin and see if it happens again?
 
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the russians were all about reliability and the though they got it right. Id get rid of the Murray firempin if your shooting milspec ammo, its usless. I have tried to get slam fire with steel cased ammo and even with round that had light primer strikes by putting it in the chamber and letting the bolt slam into it over and over again(9 times if I'm not mistaken) and it never went off. The only reason to use a Murray's firing pin is if your shooting hand loads or commercial brass cased ammo especially anything American.
 
Of the shells I do have from a previous shoot, the primers were well hit. It's just this latest time that I had a few light strikes and it was because the pin was jammed back with primer bits. One thing I do agree with, as long as I'm using surplus rounds I'll be using the Russian fp. Guess I'll have to do another 80 or so round test. Now let's pay what if. What if I'm still getting popped primers?
 
What's a "popped" primer? I know "pierced" (a hole punched in it from the firing pin, but the primer is still in the primer pocket) and "blown" (the primer in no longer in the primer pocket).

A pierced primer can occur if the firing pin has a tip that is too "sharp" and/or if it protrudes too far, and/or if the primers are exceptionally soft. Blown primers are typically from extremely high pressure and/or loose primer pockets.
 
The SKS functions fine with the factory free floating firing pin, stupid simple and reliable system. Murray's spring loaded firing pin is a solution to a nonexistent problem. Go back to factory configuration and perform regular maintenance between shooting sessions.
 
You folks are far too quick to conclude that the Murray's Firing Pin is to blame. No pics, a vague description, and no saved "evidence" leaves a lot of questions in my mind. The "logic" that since this occurred after the pin was installed mean it's the culprit is flawed. What about the bolt "improvements", are the metal pieces primer fragments, was the pin installed correctly, etc.?
 
Canadian_Zuk said:
The SKS functions fine with the factory free floating firing pin, stupid simple and reliable system. Murray's spring loaded firing pin is a solution to a nonexistent problem. Go back to factory configuration and perform regular maintenance between shooting sessions.
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Yup yup ^^^
 
Andy said:
You folks are far too quick to conclude that the Murray's Firing Pin is to blame. No pics, a vague description, and no saved "evidence" leaves a lot of questions in my mind. The "logic" that since this occurred after the pin was installed mean it's the culprit is flawed. What about the bolt "improvements", are the metal pieces primer fragments, was the pin installed correctly, etc.?
Click to expand...

I didn't realize I had a problem until I went home, that's why no pics of the shells. I'm not going on an hour long drive to find shells in the grass. My apologies on the terms, but it would appear pierced primer would be the correct one. The pin was installed after the very first box of MFS fired, so it been there since pretty much day one. The pin was installed directly too. As far as the bolt face goes, basically all I did was deburr it. Pics up in a sec.
 
weasel1 said:
I didn't realize I had a problem until I went home, that's why no pics of the shells. I'm not going on an hour long drive to find shells in the grass. My apologies on the terms, but it would appear pierced primer would be the correct one. The pin was installed after the very first box of MFS fired, so it been there since pretty much day one. The pin was installed directly too. As far as the bolt face goes, basically all I did was deburr it. Pics up in a sec.
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i was going to say check your fired brass but see you left it at the range for someone to clean up
 
Here's how I found the bolt. Notice something stuck in the fp hole:



What came out of the bolt when the firing pin was removed. Non magnetic.



Shells from a previous shoot. Don't think it really helps here, but I thought it would show the impact marks on the primers. These are Romanian surplus, the Norinco's looked exactly the same.




To me, it looks like the fp hit, stuck to the primer and sucked the pieces into the bolt. I will ask again though, if I continue to get pierced primers with the Russian pin, what is my next course of action?
 
Just fired 20 rounds with the Russian pin in. All went bang with no signs of a pierced primer. Three shells did have a really light hit on them though.

 
If you want to upgrade your SKS just todd in the Wolff SKS upgrade springs and you are good to go. DOn't waste your time with that Murray's firing pin.
 
Again, it's not in there now. Trigger work is already done. I don't see how that helps my current situation. If I had consistent light strikes it would make sense, but 3 light ones in 20? I'm just trying to grasp what's going on.
 
Man, the hole on the face of the bolt looks big! Never had a problem with factory firing pin, surplus or American Eagle , still goes bang.
 
Ok but how much of the firing pin is sticking out of the bolt face , when the firing pin is push/held all the way forward. I don't know what the spec. is , but I'll guess its sticking out way too far.... Or not , but that would be the first thing I would be looking at.
If the hole is too big ( on the front of the bolt face) it will allow the firing pin to go too far forward and causing primer pops. The mil spec stuff is a lot harder, = more resident to primer pop.
Hope this might help, someone on gunnuts will have a standard spec for firing pin protrusion.
Cheers
Brian
 
Pierced primers have many causes. I think we can rule out oversize FP hole. Excessive protrusion is possible if the taper in either the bolt or Murray's pin has worn. Measure each and compare. Another possibility is wear on the tip of the Murray's FP. Compare against the original.
 
I could see no signs of wear on the Murrays pin, but I will double check. I'll get some measurements on the pin protrusion as well just for good measure. One thing bothers me though. How come I am getting random light strikes? I am starting to wonder if the pierced primers were from the rounds that were rechambered. The brass in the primer was weak from the first hit and then finally gave on the second try. So if that's true, it explains a whole bunch. All I'd need to do is figure out why I am getting the random light strikes. I wonder if there is something going on in the trigger group. The only other thing I could think of is some fod in the bolt. I have to work all weekend, but I promise I'll get some pics of the firing pins in question.
 
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