Gunsmithing broken retaining pin in firing pin assembly

[boudin]

So last night I was taking my Remington 700's firing pin assembly apart and when I tapped the pin holding the cocking piece and f.p. together, it came out in two pieces. Is this common? I've looked on brownells, but all I see is a bolt stop pin, not this one. Does anyone have any suggestions? I guess I could go down to fastenal and try to get one the same size.

 

[Dans40X]

Re: broken retaining pin in firing pin assembly

Purchase & cut a 3/32"(.0935) drill bits shank to approximately 7/16"(.4375") length.
Or oil hardened drill rod if you have some on hand.

The striker cross pin in your aftermarket f-pin assy was a dowel pin-too hard/brittle for the application.

Insert striker cross pin from RH to LH side & insure the pin doesn't protrude out one side or the other & bind inside the shroud.

 

[boudin]

Re: broken retaining pin in firing pin assembly

Thanks for the help. It was actually the stock firing pin assembly, dowel pin included.

 

[Keith Johns]

Re: broken retaining pin in firing pin assembly

Take your cocking piece and put it on your firing pin, away and free of all other parts. Line up the holes and look through. Pushing hard on the cocking piece so its bottomed out, see if the holes line up. If they do not; if the cocking piece hole is lower on the firing pin than its hole(meaning it went past it), that I think is your problem. Its fixed by putting a small piece of steel or bedding between the f-pin and cocking piece socket, so the holes line up when there's hard pressure pushing them together.

Seen it happen. Doing that seems to take care of it.

 

[Alan Warner]

Re: broken retaining pin in firing pin assembly

After you get the repair done, stop dry firing without a snap cap.

Alan

 

[Keith Johns]

Re: broken retaining pin in firing pin assembly

So were the holes lined up or did they pass eachother like I said?

Curious what the problem was.

Might try using cross pins from PTG, theyre like $.75 each and work great for me as long as I check for what I stated above. I experienced a broken cross pin like you did, and since doing that fix, Ive never had the problem again.

 

[boudin]

Re: broken retaining pin in firing pin assembly

Keith,
I ended up cutting a pin from a 3/32 bit like Dan suggested and put it back together before reading your post. I've been too busy to pull the firing pin assembly back apart to check for sure, but judging from this picture that I took when disassembling the bolt, it looks like you hit the nail on the head. Especially considering I am not applying any pressure on the cocking piece there and you can still see the lip of the hole in the f-pin. If this is indeed the problem, I'll probably go with the devcon fix like you suggested, since I have it on hand. Thanks for your help; I'll let you know what I find.

 

[eddief]

Re: broken retaining pin in firing pin assembly

3/32" grade 8 alloy dowel pin 7/16" long from MSC work great. You're not going to shear one.

 

[Keith Johns]

Re: broken retaining pin in firing pin assembly

Boudin,
Kool. Devcon works but is more time consuming and it can crack. A small piece of steel wire that has been flattened in a vise works just as well or better and takes minutes. If you can get the holes to line up correctly with a "shim" between the two surfaces mentioned before, and hard pressure pushing them together, that wont happen again. With any strength cross pin.


A stronger pin may "fix" the problem for a year or so but with enough use any pin will break if the before mentioned problem exists.

PS, the hole line-up in the pic doesnt look too bad. I've seen them so bad it created a half moon. But, not lining up is not lining up. And 100% of the pressure caused by the cocking pieces inertia is on the cross pin.

 

[boudin]

Re: broken retaining pin in firing pin assembly

I ended up putting the school work aside last night and took the f-pin assembly back apart. The holes were indeed mis-aligned, but not by much. Still... like you said, not lining up is not lining up, so I put a dab of devcon on the end of the f-pin and let it harden overnight. This morning I sanded it down until the alignment was satisfactory and also took the time to sand and polish my firing pin, as well as polish the cocking ramp and nose of the cocking piece. The bolt lift is noticably smoother now and the holes are in line.

 

[Keith Johns]

Re: broken retaining pin in firing pin assembly

Nice work.

Dont hesitate next time to just use a piece of steel. Just put a flattened piece of steel wire between the surfaces. It cant go anywhere and wont ever crack/chip/smash.
When determining size of it, and when putting the cross pin back in, I make sure the cocking piece is pushed hard against the steel shim I made, with that hard against the firing pin. If there's any slop, it wont fix it.

 

[boudin]

Re: broken retaining pin in firing pin assembly

So, having now spent some time behind the rifle after the fix, I thought I'd share an unintentional result of the work, that I thought was interesting.

In the 2-3 months prior to this fix, I had been noticing intermittent instances of creep arising in the pull on my Shilen trigger. It seemed to happen most frequently in conjunction with forcefully closing the bolt, but still didn't really follow any pattern of occurrence. I flushed the trigger assembly with lighter fluid a couple of times, but that didn't help.

So, fast forward to the present... it appears that the creep was somehow related to the broken pin/ hole alignment. Once I reassembled everything, I noticed that the pull was a bit heavier and now, after 85 rounds and loads of dry firing I've been unable to reproduce the creep.

I'm assuming that the broken pin was allowing for the slightest shift in the sear/cocking piece interface = creep.

Anyways, just thought I'd share that in case anyone finds themselves in the same situation.