Model 34

[Legacy Defense]

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?

 

[wheelgun610]

....wouldn't it have always been this way , and not just recently?

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

 

[Legacy Defense]

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

 

[Hondo44]

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?

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.

 

[Legacy Defense]

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.

 

[Hondo44]

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.

 

[Hondo44]

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.

 

[Legacy Defense]

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.

 

[ironmikevelocette]

misfires/ firing pin problems/ model 34

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

 

[H Richard]

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

 

[Hondo44]

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.