How to ... replace firing pin model 34

[crsides]

I am getting misfires in my model 34 vintage 1972. This has been a problem for awhile that I have attributed to tight chambers and not seating the rounds completely. I polished the chambers which helped chambering rounds, but the misfires continue. It does get worse after firing a couple cylinders full.

I replaced the mainspring but no help. I got an firing pin from S&W, now I need to know how to replace it.

Any help is appreciated.


Charlie

 

[HEADKNOCKER]

Is it a frame mounted firing pin or a hammer mounted??
Gary/Hk

 

[HAM]

crsides, I have a34-1 but have never had to deal with the firing pin, but have been troubled with tight chambers also.

Take a look on either side of the frame in the area of the firing pin and notice the heads of a tiny pin. I'm fairly certain that one would have to drive that pin out to release the old firing pin assembly. Looks like a delicate but doable operation to me. They sell cupped pin punches (Brownells) that I think you would need in order not to damage the pin or the finish. BTW, I am noway a gunsmith or anything like one.

Would like to know how it goes if you do replace it. Good luck.

HAM

 

[ViperR]

I was getting some misfires on my 70's 34, also. What I found was exessive endshake and one .002" washer from Power Custom did the trick. Now after over 1000+ rounds, every round fired.
Now the tricky part. There is no bearing made for the rimfire j-frame (centerfire j-frame won't work). You have to get some for the k-frame and turn down the o.d. to fit in the cylinder. Easy to do with a pencil & emery cloth.

 

[cush]

I agree with Viper. I have a late 1950's model 34 that had consistant misfires. Mine was caused by excessive endshake as well. According to my gunsmith (that I trust) he said it would be HIGHLY unlikely that a firing pin would fail, and if it did it wouldn't fire at all.

Check your endshake. I sent mine back to S&W and they took care of it for me.

 

[crsides]

Thanks guys.

HEADKNOCKER - It is frame mounted firing pin.

I will hold off on the firing pin replacement and deal with the endshake. So endshake is the fore and aft movement of the cylinder. If too much endshake, the firing pin has to drive the cylinder forward, then crush the primer. or is it that the cylinder could be positioned too far forward, effectively making the firing pin too short for the cylinder position. Do I have this right?

Can you measure endshake by holding the cylinder to the rear and measuring bbl cyl gap and then do the same with the cylinder held forward? What should the min/max measurement be for this?

I am just trying to think this through. Appreciate any and all guidance.


Charlie

 

[crsides]

checked for endshake on the mod 34. NO movement whatsoever when the cylinder is closed. There is some play when the cylinder is open, but that looks ok as the rear mvt is stopped by a protrusion on the frame.

Back to firing pin?


Charlie

 

[JcMack]

Have you tried different brand of ammo? .22 cases should have nice dent in the rim. Have you compared fired case rims? If gun was dry fired a lot there will be associated "dimples" on the cyl. face. That will cause misfires. I'm not trying to insult your intelligence with these comments. It does sound like FP issue.

 

[Dan Cash]

Do be sure to check you ammo. I have run into some Remington ammo that flat would not fire in anything. Lots of ammo has gotten very crummy in the last couple of years. Perhaps it is the low lead priming?

 

[ViperR]

I also agree with trying several types of ammo. There could also be the possibility that crud has accumulated in the FP bushing channel that is keeping the FP from fully extending. Blast it clean with Gun Scrubber and compressed air and shoot again. There is the slight chance that dry-fire damage is there, but S&W designed their rimfires so the FP only goes so far out and doesn't reach the cylinder recess where the rim of the round rests. If they made the FP longer, They would be constantly replacing them from dry fires. I do not dry fire my rimfires though, and always use spent cases for that purpose.
Try the simplest and cheapest things before the tricky task of FP & bushing replacement.

 

[crsides]

I use to shoot the cheapest stuff round, but since trying to diagnose the problem I have fired cci std, wolf match target, fed 510 with same results ( or worse).

Will try blasting the firing pin hole channel with gun scrubber and compressed air. Always go for the easiest, cheapest first.

Charlie

 

[crsides]

I did the gunscrubber & compressed air thing, but did not see any additional forward mvt of the firing pin. I purchase a new firing pin from Brownells, and it was .004 short of the old one. Thought I would give it a try so installed the new shorter firing pin. Will test it out next time I get to the range. that could be a while.


Charlie

 

[scooter123]

Two more things to keep in mind.

One is the 22LR is a rifle cartridge and there are compromises to using it in a handgun. That is that it's distinctly dirty to shoot and will foul the chambers in the cylinder faster than a centerfire handgun caliber. I probably spend twice the time cleaning the crud off of my 617 than any other handgun I own and I believe it's because of the unconsumed powder due to the shorter than optimal barrel. I scrub the cylinder in my 617 out after 100 rounds fired because not doing this makes it difficult to fully seat some rounds. Any standoff from fully seated will greatly reduce ignition and cause misfires. BTW, it took me a few trips to the range to pick up on that.

Second, I don't know of any rimfire ammunition that approaches the cost of a centerfire caliber. In the case of bulk ammunition, the cost per round is nearly as cheap as a small pistol primer. With the cost being this low, it's not a real shock that 22LR may not be 100% reliable in terms of ignition.

The good news is that it is cheap to shoot and pretty accurate as well. I've been running Winchester Xpert HV in my 617 and the rate of misfires is about 1 in 100 rounds downrange. After rotating the misfires and trying again, I've only had one that failed to fire on the second time around. I'll also note that almost of all my misfires have taken place on the second box of 50, which means that I should probably start taking a brush to the range.

 

[DCWilson]

One more last minute suggestion: if the ejector star has any fouling beneath it, then internal spring pressure may not be enough to keep it from standing slightly proud of the back surface of the cylinder. When the hammer falls on the cartridge, it can waste some momentum pushing the cartridge AND the star back into position before the rest of its momentum -- which may not be enough -- crushes the rim of the cartridge and tries to ignite the primer.

In any gun cleaning, particularly of revolvers that have a chance to foul easily, I advocate removal and disassembly of the cylinder group to give it the best possible cleaning. At the very least you should drip some serious solvent down the ejector star shaft and work the plunger in and out a lot, as well as giving a good toothbrush scrubbing to the back side of the star and a toothpick or dental pick scrape to the edges of the ejector star recess between the charge holes. Give the same toothpick treatment to the rim space inside each charge hole; these spaces always gum up in .22s, and the gunk does not easily come out with the usual post-shooting scrub and wipe-down. Even the cleanest and least-shot .22s I have ever bought needed this kind of attention to detail on the charge holes.

Good luck. FTFs are some of the most annoying problems to diagnose and fix.

 

[H Richard]

No one has mentioned the mainspring. If you are not the first owner, check and see if the mainspring has been cut. With the cylinder open and the cylinder release pushed back and holding a finger over the recoil shied where the firing pin bushing is, cycle the action and see if the pin "bites" you enough to be a reliable hit. A previous owner may have done a "trigger job" by cutting a few coils off the main spring. Also trying several different brands of ammo may fix it.

 

[JcMack]

No one has mentioned the mainspring. If you are not the first owner, check and see if the mainspring has been cut. With the cylinder open and the cylinder release pushed back and holding a finger over the recoil shied where the firing pin bushing is, cycle the action and see if the pin "bites" you enough to be a reliable hit. A previous owner may have done a "trigger job" by cutting a few coils off the main spring. Also trying several different brands of ammo may fix it.

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