You mentioned some trigger work? Could you elaborate on what's been done. When I do my SKS triggers I cut two coils off the hammer spring and have had zero issues with light strikes and surplus ammo. I have no idea what kind of springs come in the "kits" but if they're intended for the US market then they may use a very light hammer spring which is ok with all the commercial X39 in the US. Factory boxer primers don't need nearly the hit that surplus berdan primers do. Another possibility is the ammo. Did you mention whether the light strikes happen with all types or just one ammo?
Pierced primers.
- Thread starter weasel1
- Start date
Just measured the pin protrusion. Murray's is .049" and the Russian fp is .054. No defects found in either pin. Murray's is slightly more rounded. I could file the Murray's pin so I get that extra .005", but I think it's unnecessary as the depth on a good strike was certainly deep enough. Visually, things were really nice inside the fp hole of the bolt. I have a theory as to what may be going on. Initially, both pins were lightly lubed before installation. I have a feeling things were gunking up. I have a sneaky suspicion that if I were to have collected my shells in order of fire, you'd find the three light strikes were the last three. I'll keep the Russian one installed while I continue to to go through this crate, without lube in the fp hole. Pics up in a min.
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Lube won't cause light strikes and it takes a very long time to gunk up. I speak from experience, not my ass. I always lube the FP. It will wear prematurely if its run dry. It may take a while but an oiled FP will last longer and does not blacken the skies with armageddon as some would have you believe. Now as to the FPs themselves, try to find a pic of a new Murray's FP to see if yours has rounded off. More surface area of primer cup pushed in means more metal being stretched. The shorter protrusion may be where your light strikes are coming from. 5 thou doesn't sound like much but its 10% of total protrusion. Me thinks Satain was right, the Murray's FP is for soft commercial primers and gets ruined by milsurp berdan primers.
Will I certainly have the technology to shape the fp tip and to get the .005 back. Still seems odd I am getting a few light strikes with the Russian pin though. At least they all go bang when required. I will take the lubing of the fp into consideration.
You can play around if you want with the Murray pin, I did and I just put the original pin back in.
The original pin only protrudes a fixed amount, has a certain geometry to the point and hits with a certain amount of force.
Once you change that, say with a spring loaded pin, a very small amount of energy, IMO, is lost overcoming the spring on the after market pin. I also tried using the reduced power hammer springs, Only a few pounds difference but it was enough to cause FTF's. So, to me, any alteration of this geometry or the transfer of the force from the hammer results in FTF.
So by adding a spring pin - no bang. By adding reduced power hammer spring - no bang. By playing with the shape of the tip of the spring pin - no bang. By leaving it stock but cleaned and polished - bang.
The details of my FTF's with the Murray pin. (I had no problems before trying the spring pin I was caught up with the worry of a "slam fire".)
I experienced "light strikes" or FTF's where the second time around it would go bang. Before that I had popped primers where an ejected disk of the primer is thrown either into the bolt face aka "dangerous condition", or the disk falls into the receiver where it interferes with the proper closing of the bolt aka "gun don't fire because bolt can't lock down". The popped primer also completely fries the spring for the FP as the hot exhaust gases enter the bolt.
The popped primers was resolved by cleaning the bolt face around the FP hole. This info found on Murray's web site and was very useful. However I never had reliable and predictable primer detonation with the Murray pin.
I would not try it or use it WITHOUT the spring.
Now I only use the original pin, keep it clean and lightly oiled. I only use surplus ammo.
The original pin only protrudes a fixed amount, has a certain geometry to the point and hits with a certain amount of force.
Once you change that, say with a spring loaded pin, a very small amount of energy, IMO, is lost overcoming the spring on the after market pin. I also tried using the reduced power hammer springs, Only a few pounds difference but it was enough to cause FTF's. So, to me, any alteration of this geometry or the transfer of the force from the hammer results in FTF.
So by adding a spring pin - no bang. By adding reduced power hammer spring - no bang. By playing with the shape of the tip of the spring pin - no bang. By leaving it stock but cleaned and polished - bang.
The details of my FTF's with the Murray pin. (I had no problems before trying the spring pin I was caught up with the worry of a "slam fire".)
I experienced "light strikes" or FTF's where the second time around it would go bang. Before that I had popped primers where an ejected disk of the primer is thrown either into the bolt face aka "dangerous condition", or the disk falls into the receiver where it interferes with the proper closing of the bolt aka "gun don't fire because bolt can't lock down". The popped primer also completely fries the spring for the FP as the hot exhaust gases enter the bolt.
The popped primers was resolved by cleaning the bolt face around the FP hole. This info found on Murray's web site and was very useful. However I never had reliable and predictable primer detonation with the Murray pin.
I would not try it or use it WITHOUT the spring.
Now I only use the original pin, keep it clean and lightly oiled. I only use surplus ammo.
From everything I have read about the Murray Pin, its only worth using if you have problems with your normal one.
Do they reduce the likelyhood of slamfires? Perhaps.
Do they increase the likelihood of other problems? Seems like it.
Do they reduce the likelyhood of slamfires? Perhaps.
Do they increase the likelihood of other problems? Seems like it.
Long ago and far away on another planet, part of my job was to answer customer complaints for a Canadian ammunition company. There were generally three things that could happen to a primer during a failure. The blown primer, almost always the result of high pressure (if you're ever sending a high pressure handload to an ammunition company hoping to blame them for your buggered gun, make sure you clean the powder residue from the case remnants); the pierced primer which results from a sharp or narrow firing pin which starts off as very intermittent then increases in frequency as the hot gases erode the firing pin and aggravate the condition; and the "blanked" primer which may have been what you referred to as "cookie cutting". This is really the only fault that would result in particles of the primer cup entering the bolt and action. It is caused by the primer not receiving enough support from the bolt face because the hole for the firing pin is too large and/or the firing pin much too narrow. You may have aggravated this condition in your attempts to prevent it. If the original firing pin is a bit larger than the after-market replacement it would fill in more of the firing pin opening, give the primer better support and solve your problem.
That is not pierced primers, that is blanking. Completely opposite of piercing. The primer is not being supported by the firing pin during it ignition and the pressure is plowing the primer through the firing pin hole.
I'm absolutely unfamiliar with this aftermarket firing pin but I suspect it's lighter than factory.
It may be hard to comprehend but that firing pin traveling at a mere few hundred feet per second (even it it is only .065") weighing only a few dozen grams with a tip surface area of about 2 thousandths of an inch actually exerts 45 000'ish psi of force.
Lighten that pin up too much and it will not have the kinetic energy to support that tiny area of the primer and it will be blown back (blanked) into the firing pin channel just as you see.
I'm absolutely unfamiliar with this aftermarket firing pin but I suspect it's lighter than factory.
It may be hard to comprehend but that firing pin traveling at a mere few hundred feet per second (even it it is only .065") weighing only a few dozen grams with a tip surface area of about 2 thousandths of an inch actually exerts 45 000'ish psi of force.
Lighten that pin up too much and it will not have the kinetic energy to support that tiny area of the primer and it will be blown back (blanked) into the firing pin channel just as you see.
Really do appreciate all the info. I am learning way more about primers than I ever thought I'd need.
Just to recap, gun was cleaned after having problems with a Murray's firing pin, Russian pin installed (lubed, lightly or so I thought). Fired 20 rounds. All went bang. Three of the shells had light strikes, but still fired first time. Kicking myself for not collecting them in order of fire. So, if the three were shots 18,19 and 20 can we blame the lube (too much, not compatible, etc)? If the three were random, then what? Or am I really over thinking this? On the grand scale of things it's a very minor problem. To me, it's like a single mosquito buzzing around your head in the night.
Just to recap, gun was cleaned after having problems with a Murray's firing pin, Russian pin installed (lubed, lightly or so I thought). Fired 20 rounds. All went bang. Three of the shells had light strikes, but still fired first time. Kicking myself for not collecting them in order of fire. So, if the three were shots 18,19 and 20 can we blame the lube (too much, not compatible, etc)? If the three were random, then what? Or am I really over thinking this? On the grand scale of things it's a very minor problem. To me, it's like a single mosquito buzzing around your head in the night.
Too thick of lube may indeed cause light strikes. As will too thick or too much combined with tight tolerances. Viscous drag. I've tested this myself disassembling, cleaning, lubing, assembling, test firing and repeat with a thin lube (triflow) back and fourth over and over. The thick lube consistently slowed the pin enough to cause a light strike and reduced it's energy enough to cause blanking. 50 rounds were fired with each lube. The heavy one blanked each and every of the 50 primers, the light lube never caused a single issue during the test or the other 5000 rounds.
Interesting. The lube I was using was fairly thick. I'd say the consistency of motor oil. I have a very light moly lube in the tickle trunk. Think I'll give that a try.
I was also reading that shellac in the chamber can cause the same effect. Don't think I've fired quite enough for that to be causing my issues.
I was also reading that shellac in the chamber can cause the same effect. Don't think I've fired quite enough for that to be causing my issues.
We are very familiar with these issues, as we work with a lot of SKSs, here is one simple fix with the boltface: http://www.murraysguns.com/poppedprimers.htm
Here is the best way to fix your SKS, neck & throat reaming, a service we offer. It eliminates high pressure spikes that pop primers or make cases stick in the chamber: http://www.murraysguns.com/neck&throat.htm
We also offer trigger jobs & firing pin installs, as well as most custom builds you would like, PM for details.
Here is the best way to fix your SKS, neck & throat reaming, a service we offer. It eliminates high pressure spikes that pop primers or make cases stick in the chamber: http://www.murraysguns.com/neck&throat.htm
We also offer trigger jobs & firing pin installs, as well as most custom builds you would like, PM for details.
