Question about firing pin / primer

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Question about firing pin / primer

Post by eagle60 on Tue Jul 10, 2012 9:55 pm

Time to draw upon the vast knowledge of the folks here..
As some of you may remember, a while back I was asking about where to find a hammer for the sks and I got some good information about locating one, however I never did get around to getting one. With the recent addition of the mill to my shop - well lets just say that I have a hammer now Smile Using all caution, I tested with an empty hull with spent primer, then a empty hull with a new Winchester LR primer, then 1 live round, then two live rounds. No unexplained (or unwanted) explosions and no slam fire. Live testing was done with rifle tied to bench and a very long string of course )

What I did notice is that the firing pin is smacking the heck out of the primer leaving a nice deep depression. From the bottom of the primer with the anvil out it looks like it wouldn't take much to punch through. These were Winchester LR primers and I'm reasonable sure that they are a little softer than the mil spec primers that were designed for this type rifle. Now, my question is this, to stay away from the possibility of punching through a primer, would it be feasable / safe to trim just a tad off of the firing pin? I'm thinking that the worst case scenario would be (a) slam fire because of a burr left on the firing pin or (b) won't fire because I got the firing pin too short.
Don't know if the pictures will be clear enough to see what I'm seeing or not...

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Re: Question about firing pin / primer

Post by Reload3006 on Tue Jul 10, 2012 10:29 pm

is the firing pin retained and retracted by a spring? If so I would replace that spring for one a bit stiffer. if that didnt solve it I would stone a thousandth or two of the firing pin from the inside or from the face of the hammer Or weaken the hammer spring.
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Re: Question about firing pin / primer

Post by eagle60 on Tue Jul 10, 2012 11:47 pm

Thanks for the suggestions. The firing pin is not spring loaded. The pin protrudes 58 thou past the face of the bolt, not sure what is considered "normal" for that measurement though. I have to take the hammer back out anyway to get it hardened and heat treated so I may try your suggestion of stoning the face of the hammer to see what that does. Lightning the hammer spring would be easy enough. I guess the only thing I would have to watch out for on that would be to not get it so light that it wouldn't fire surplus ammo with harder primers.
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Re: Question about firing pin / primer

Post by algunjunkie on Wed Jul 11, 2012 1:50 am

.058 is within normal specs for this type of weapon system. If you were not having this issue before then I would suggest that the fix is the problem. If yo had this problem before then there could be a whe list of things that are going on. If you choose to go the way of the firing pin then proceed with caution and test often because a little bit goes a long way.

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Re: Question about firing pin / primer

Post by tripples on Wed Jul 11, 2012 3:43 am

Why not try to lighten the hammer a bit, that way its not nailing the firing pin as hard. Or perhaps your dimensions are slightly larger than needed.

Where did you get the dimensions to make your hammer? Hell if you need dimensions I can probably get them for you even if I have to pull the trigger group apart.

By the way I like the fact that you took the time to make it yourself.

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Re: Question about firing pin / primer

Post by eagle60 on Wed Jul 11, 2012 6:16 am

Thanks for the fp spec. algunjunkie, wasn't sure about that the spec, I haven't given it any thought until now. I didn't notice it doing it before but that doesn't mean it wasn't doing it. I had thought about one of the Murrays spring loaded firing pins but I've heard pros and cons about using them, Have you had any experience with them?

Thanks tripples, I borrowed one from a friend and got the specs for final dimensions. I guess it could be a tad heavier than the original, I haven't weighed them. His was .421 from the face to the back and that was the thickness that I ended up with.
Heck, I had to have a "first project" for the mill and this seemed like a good place to start Smile
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Re: Question about firing pin / primer

Post by Rick459 on Sun Jul 15, 2012 3:02 pm

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Re: Question about firing pin / primer

Post by eagle60 on Sun Jul 15, 2012 6:56 pm

Thanks for the links Rick, I'll have to take a good look the the bolt again. Have you had any experience with the Murrays firing pins?
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Re: Question about firing pin / primer

Post by Rick459 on Sun Jul 15, 2012 9:34 pm

eagle60 wrote:Thanks for the links Rick, I'll have to take a good look the the bolt again. Have you had any experience with the Murrays firing pins?

my girlfriend has a yugo and for awhile there she was getting pirced primers using wolf classic 7.62x39 which in turn bent her firing pin. sent the bolt to murray's and he installed one of his rebounding firing pins and did some bolt work and that fixed the problem. if the firing pin does not pierce the primer you should be ok. i would remove metal from the pin tip and then re-temper the pin.
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Re: Question about firing pin / primer

Post by eagle60 on Sun Jul 15, 2012 10:25 pm

Thanks Rick. That gives me a couple of things to check. I hope that a little fine tuning will correct the problem, and if not I will plan on getting the Murrays firing pin. Thanks for all the responses guys!
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