I am a new Gunsmith, working on a model 34 that doesn't always fire, DA or SA. The firing pin strikes are VERY light. I have swapped out the hammer spring and that didn't fix it. I suspect the firing pin is worn down.

Does anyone have the length that the firing pin should be so I can check it?

Does anyone have a firing pin I can buy?

Am I on the right track?

I have checked -
Numrich
Brownells
Emailed Outback, waiting for response
Emailed gunpartsauction - waiting for response
Will call Jack First in the morning

Thanks in advance.

Welcome to the forum. I'm just north of you in Fresno.

The light strike is because the round did not discharge and slam back against the firing pin.

The 1st thing I always check is for gunk in the firing pin bore in the frame, and flush well with a spray cleaner.

Is there excessive headspace because the cyl has forward and backward movement or "end shake". Shimming the front of the cyl is the solution for that.

Whats' the serial #? There are two styles of firing pin, round and rectangular.

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Jim
S&WCA #819

The firing pin should be removed and inspected to be sure it hasn't broken, and is in two pieces. If so it will not strike as hard. If the firing pin is not square on the tip it should be squared up to strike properly.

Sometimes the coil spring will need a shim to increase it's tension.

Sending you Private Message for parts sources.

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Jim
S&WCA #819

sn = 14443

Even the ones that did fire look like light strike.

Check to make sure that the firing pin isn't worn down from
excessive dry firing caused by the firing pin hitting the back of the cylinder.

Stu

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NRA Benefactor/Cert Instructor

That is why I asked if anyone knew the length the firing pin is supposed to be, so I can check it.

It's not unheard of for D/A rimfire revolvers to accumulate enough gunk under the extractor star to cause light hits from the firing pin. The junk under the star acts as a cushion at the moment of truth and ignition can be inconsistent - or totally non-existent.... I've had that happen with a couple K-22's - which have basically the same firing pin set up as the Kit guns.

Might be worth a shot - if you haven't already given the whole thing a good detail cleaning....

Mark

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S&W Forum Member #721

Thanks guys, I will start with a detail clean and see if the firing pin is broken.

Kinda funny that i didn't detail clean it first (this time), I have been doing that (above and beyond what customers asked for, no extra charge of course) as a way to "practice" and become more familiar with the guns...

Keep us posted. We'll figure it out - one way or another.

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S&W Forum Member #721

One other possibility is a carbon ring in the chambers preventing the cartridge from being completely seated. Then when struck by the firing pin it drives the cartridge forward until it is seated, but that movement took all the energy form the strike. Double check the rounds are able to be completely seated. Will the round fire on the second attempt (without removing it from the cylinder)?

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H Richard
SWCA1967 SWHF244

Did you mention whose ammo you are using? Mike 2796

I doubt if anyone has one out of a gun to measure, but there's probably enough variation after they get fit in the gun to not be of much help, and one reason I asked for serial # to get the vintage and round or rectangular firing pin tip.

You need to check the firing pin protrusion from the breechface, which might be more revealing. Here's how I do it, you may have a better technique.

With gun in left hand, (if you're right handed) cock the hammer and lower it all the way forward while holding the trigger all the way back to disengage the hammer block safety bar. Open cylinder and measure between the forcing cone end of the barrel and the protruding firing pin tip.

Now release the trigger and measure from end of barrel to breechface. The difference between those two measurements gives me a .030" tip protrusion on a 1957 vintage, New I frame, M34 with rectangular tip firing pin.

If the gun you're working on has a round tip firing pin, I can get a measurement for that style to verify if they are different.

Hope this helps,

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Jim
S&WCA #819

Detail cleaned, inspected all parts, rectangle firing pin. Jack First measured their firing pin and it was .378, this one is longer. 2 out of 6 rounds Don't fire.

I will measure protrusion when I get home, but if 4 fire...

What do I look at now?

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Jeff
CCW Instructor, FSC, FFL

Do the rounds drop into the chambers without resistance? Is there any 'end-shake' in the cylinder when the hammer is in the fire position?

I'd probably try a couple other brands of ammo, too. It's not just .22 revolvers, but many .22's will fire/function more consistently with some brands better than with others.

Mark

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S&W Forum Member #721

Rounds drop in fine

Currently testing with Winchester wildcat but also tried CCI Minimag(customer provided) I told him he should use standard velocity.

End shake is about .004-.005

Firing pin protrusion .013? That can't be right according to what hondo44 said about his being .030.

I am going to get a different micrometer and see if I can get a better measurement.

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Jeff
CCW Instructor, FSC, FFL

I have four Pre Mod 34s and three Mod 34s, all different vintages, and they all shoot any available .22 ammo reliably.

Are there any marks on the sides of the hammer where it might be dragging against the frame?

"Sometimes the coil spring will need a shim to increase it's tension."

Sometimes the firing pin just needs a bit of sharpening.

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Jim
S&WCA #819

Thirteen thousandths of an inch is definitely NOT a deep enough punch. That is not enough strike to ignite the round. You just have to figure out what's keeping it from punching deeper and you'll have it.

Bingo! That's clearly the problem! The least protrusion on any of my M34s is .026".

Endshake is a bit much and I'd shim the cyl. But that firing pin is the issue.

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Jim
S&WCA #819

I need to find another way to measure the protrusion, my caliper can't get a straight on measurement because of a knob on it.

I measured the firing pin yesterday and it was longer than the one Jack First Measured so I am confused...

It seems reasonable that the firing pin would be worn down though.

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Jeff
CCW Instructor, FSC, FFL

Jeff,

Can you unscrew the knob on your caliper, is it just the slide lock knob?

I can't put much faith in the length of another pin. It's a beginning indicator but kind of irrelevant to how it will perform once fitted to a gun which are all slightly different due to manufacturing tolerances.

I still think the focus should be the protrusion of the pin from the breech face. That's where the rubber meets the road. The hammer nose bushing (recoil plate) with the firing pin aperture may not be drilled deep enough on the hammer side.

Worn firing pins are so very uncommon on S&Ws. I've had so many Smiths from 150 years old to newer and never needed a new firing pin because one was worn, especially a 22 that only strikes brass.

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Jim
S&WCA #819

Ok, I got a better measurement for protrusion, .028

Hondo44 - if what you were talking about below was true, wouldn't it have always been this way , and not just recently?

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Jeff
CCW Instructor, FSC, FFL

Hmmmm..... I was gonna ask you a couple questions along those lines....

First, what's the vintage of the gun? (S/N, including letter prefix)

How long has your customer owned the gun, and how long has this problem been going on? Has the customer tried to repair it before he/she brought it to you?

Mark

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S&W Forum Member #721

Serial number is below in another message, no attempts to repair before coming to me.

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Jeff
CCW Instructor, FSC, FFL

Jeff,

OK, the protrusion is good.

That's a very good question. Here's what I've found in fifty years of gun collecting: this gun may have had a problem from new. Guns like this can be traded and/or resold over and over again, each new owner realizing the problem and then dumping it on someone else. Is the gun in pretty good condition w/o a lot of indication that it's been shot a lot?

Or former owners have done as someone posted above, found a brand of ammo that shot more reliably and just stuck with it.

Is this gun new to the owner or did it all of a sudden start miss-firing?

I still would shim the cyl and get ithe end shake in spec. And if it still miss-fires, shim the coil mainspring or find an after market stronger spring.

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Jim
S&WCA #819

The owner bought it long ago, it hasn't been shot much and is in great shape, It is a new problem. I ordered cylinder shims from one of the places you sent me info for and I will also shim the spring.

The spring that I initially swapped out was the original spring from my wife's 642. When I was looking around for springs it appears that they may be the same so I figured I would try it.

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Jeff
CCW Instructor, FSC, FFL

Well that is a mystery if the owner's memory is correct. Because you'd expect to find a 'smoki'n gun' like a broken part if the problem just started.

That was a good thought, I would have done the same, swap in a spring that I knew worked well.

I've become convinced a rim fire is harder to discharge then most center fire primers and especially .22 WRMs.

I'll have to check part numbers on rim fire mainsprings vs. center fire springs.

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Jim
S&WCA #819

Hi Jeff,

Did you ever figure out the cause of the mis-fire issue?

All the sources I was able to find indicate the I and J frames/rim fire and center fire all use the same coil mainspring # 5749.

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Jim
S&WCA #819

Yes, sorry I neglected to post it, got more guns in and life etc...

Thank everyone for their help!

I used the list of suppliers and found the shims I needed for the cylinder, end shake is gone, problem is not. As I stated earlier I used a stock mainspring from a 642 before and that didn't help either. Final step was to add a washer to the mainspring that was already in the gun. NOW it appears to work, finally!

This was quite a learning experience and I really appreciate the experience (and suppliers list) that you all contributed to this.

Thank you.

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Jeff
CCW Instructor, FSC, FFL

use a feeler gage to check the cylinder to forcing cone gap in all positions. inequalities indicate a bent extractor rod. if this fault is found, also check yoke alignment. on centerfires the firing pin impressions will be variously off center and of differing depths. i don't know what kind of visual clue a rimfire might exhibit. try firing six rounds and look carefully at the impressions before ejecting the cases.
a transfer gage for measuring firing pin protrusion is described in kuhnhausen's mauser shop manual. this is a rod inside a tube of equal length with a friction device.the assembly is pressed against the protruding firing pin. subtracting the length of the tube/rod from the overall gives pin protrusion.
good luck,
iron mike

I think the mainspring for a 34 might be different than for a 642.

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H Richard
SWCA1967 SWHF244

On airweight guns, Smith has sometimes used heavier springs for reliable ignition due to lack of mass on the lighter guns. But not in the case of the 642. The only current models I can find with different springs are the Models 650 & 651 which are full weight but chambered in WMR.

This cartridge is notoriously harder to detonate, so it's most likely a heavier spring, # 076020000. All other J frames use # 071040000 including the M642, and is also listed for the obsolete Model 34.

When the 642 spring didn't work, and everything else checked out OK, I figured shimming the spring as suggested early on was the only cure. the spring # 076020000 would probably work.

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Jim
S&WCA #819