Help me figure out why my new SKS is popping primers?

[GJgo]

Generally, yes, you need a headspace gauge. I'm not really being that picky here though. With a stripped SKS bolt & no carrier installed you can actually use a feeler gauge between the case head & the bolt face pretty easily. You can a) feel if the bolt locks up tight or loose, and b) feel if there's any gap between the bolt face & the case head.

So, my bolt locks up well, with just a couple thou play in its cradle. Next I tried this both with a live round (3 different types) and also fired brass (2 types) and in each case the bolt locked up tight, and I could not get my smallest .002" gauge between the bolt face & the case head. There was no movement of the round at all in any case so I'd say headspace is good to go.

Edit, had a thought here on why some of my fired brass shrunk at the shoulder, and maybe also why those primers popped. The test above tells me that my headspace isn't too loose. But, what if it is still too tight & the bolt isn't fully locking up? So I grabbed my feeler gauges again. With the stripped bolt (only) locked into battery I have a .008" gap between the barrel & the bolt rim. Next, with a live (Hornady) round chambered it had a .011" gap- aha! It would appear that my bolt face needs roughly .003" removed to allow the bolt to "fully" lock up. Seem reasonable? The "lock up" on the back of the bolt is an angled ramp, so it's sliding into battery, but not sliding 100% in it would seem.

 

[GJgo]

Well, I had some down time so I've rounded off the firing pin tip & stoned the bolt face so it's smooth now, which removed the high spots & eliminated that ugliness around the FP hole. I think it came out great. Here's a photo of the work w/ the original pin. THR won't let me upload it now (??) so I'll try it this way.

I also got Murray's FP so I'm going to try it along side the original one with various types of ammo to see how it runs. My trigger is off at Kivaari's though so I'll report when it's all back together.

 

[GJgo]

Ok update. I got the trigger back form Kivaari, vast improvement. 4 lb pull now with very minimal creep. I also did some testing of the original vs. Murray's firing pin. No difference in how the primers look (they look fine now that I stoned the bolt) however the sprung pin doesn't always light off the hard primers on the first strike now. I'll probably put the original pin back in if I'm shooting the cheap stuff.

Only real issue now is that the primers are still backing out a bit. I'm wondering if my bolt being a couple thou from full lock up when a round is chambered could be causing the bolt to unlock a little too fast, perhaps allowing the primers to back out a bit. I really don't think it's a problem, just thinking about it..

 

[musicman10_1]

I bought one of Murray's firing pins with the springs and then I had problems with popped primers and debris getting into the firing pin channel and obliterating the springs. He sent me more springs but at this point I'm ready to ditch the spring loaded firing pin altogether and go back to the original pin.

 

[GJgo]

As it turns out blown primers did destroy my FP spring on the Murray pin & clog up the channel. Moving on, I'll save that unit for handloads & keep the original pin in for the hard primers.

--------------------------

Ok I think I finally solved the last issue- the firing pin protrusion was too long. It was around .055-.060". After talking to Murray, who said it may help to go as short as .045", I did, and voila no more blown primers with any brand of ammo I was testing- both with the gas block on & off. I'm going to call it good for now unless something else pops up.

 

[TheLostOtter]

Wish I would have seen your thread 2 months ago when you were having issues. My "brand new" Yugo was popping primers like this when I first got it. Everyone was saying it needed Murrays firing pin and a new bolt. I shortened the firing pin slightly, rounded it off just like you did, then polished it to get it perfectly smooth. Haven't had one popped primer since (been almost two years).

 

[GJgo]

Thanks Otter. I'm not too upset about having a spare firing pin in the drawer so I'll chock it up to experience. Hopefully the next guy will see all this first.

 

[clone]

The murray firing pin is a band-aid fix for lazy people that don't want to clean the firing channel every once in a while.

I have 3 SKS's and none of them has ever had a slam fire. I even bought one of my SKS's (for $100 because he was afraid of it) from a guy that had it slam fire on him a few times. It was caked with crusty cosmo and after a cleaning and several thousand rounds it has never slam fired....ever.

I gotta hand it to murray though they are makeing a living off of those people.