Model 34

[Legacy Defense]

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.

 

[Hondo44]

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.

 

[Hondo44]

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.

 

[Legacy Defense]

sn = 14443

Even the ones that did fire look like light strike.

 

[Stu1205]

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

 

[Legacy Defense]

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

 

[wheelgun610]

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

 

[Legacy Defense]

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...

 

[wheelgun610]

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

 

[H Richard]

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)?

 

[gmborkovic]

Did you mention whose ammo you are using? Mike 2796

 

[Hondo44]

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

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,

 

[Legacy Defense]

Update

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?

 

[wheelgun610]

....What do I look at now?

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

 

[Legacy Defense]

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.

 

[Hondo44]

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.

 

[rgm36]

firing pin

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.

 

[Hondo44]

End shake is about .004-.005

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

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.

 

[Legacy Defense]

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.

 

[Hondo44]

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.