Model 65 Firing Pin

[OldDragon30]

My first post... be gentle with me.

I have a Model 65-1. It has been tuned by a good gunsmith:
- Timing corrected
- Trigger tuned
- Trigger smoothed
- Cylinders chamfered

The gun has a lot of misfires, which appear to be light strikes. In almost all cases, the "misfired" cartridge will fire on the second strike.

I also have an older Model 10. In comparing the two pieces, something jumped out at me. The firing pin on the Model 10 protrudes through the frame significantly farther than on the Model 65. I say "significantly" because I haven't measured it, but, it is clear even to the naked eye.

My question is this: could the chamfering of the cylinder and the "short stroke" of the firing pin account for my misfires? The answer seems an obvious "yes" to me, but, wanted to check on this forum before taking the gun back to the 'smith.

Thanks.

 

[murphydog]

Welcome! There are several experienced gunsmiths here, but my non-mechanical mind would check to see if the mainspring tension screw on the front strap is snugged all the way in. If it had a lighter mainspring put in that might also explain your problem, along with crud buildup in the frame channel where the "hammer nose" (aka firing pin) rides. Others may have better ideas. Hope this is helpful.

 

[M29since14]

Good advice above. Did you ask your gunsmith if he test fired the gun?

Chamfering the charge holes, if done properly, would not cause your problem. Since you haven't measured firing pin protrusion, and without knowing the factory spec, it is hard to say on that. Does the firing pin (called "hammer nose") appear to be rough or broken?

 

[OldDragon30]

Thanks to all for the advice and guidance. Update:

I cleaned and inspected the firing pin channel and found no obstructions, debris, or residue.

The cylinder is both chamfered AND recessed. However, the cylinder fits very tight to both the breech and the frame. There does appear to be some end-play which concerns me.

As best as I could, I measured the protrusion of the firing pin on both the 65 and the 10. Pretty much identical when measured empirically using a micrometer. The eye is a poor instrument. My apologies for misleading the group on that.

On the statistical side of this, 10 of 59 cartridges misfired during the last match. In IDPA, that equals a very bad day. The ammo is my own: 125 gr lead, 3.8 gr Unique, Winchester primers. I compared the primer strikes on the misfires to the cartridges that did fire. Using my clearly defective "measuring eye", they appear to be very different.

At this point, my next immediate step is to take the same batch of ammo to the range and fire it through one of my other two unmodified Model 10's. If I get the same result, it's very likely my ammo. If not, then the 65 goes back to the gunsmith with the misfires for evidence.

Any other advice or guidance is much appreciated.

 

[chief38]

No offense to the few QUALITY GUNSMITHS here & still around, ............. but I have found them to be few and far between! If a GS has had at the gun in a serious way there is no telling exactly what the problem is over the internet. You will have to FIND one of the REAL GS's to determine exactly what the problem or problem's there are.

Two things I have learned about guns.......
1) Never buy one that has been "smithed".
2) Always do my own smithing. If I screw it up I at least know who to blame and I know exactly what I did.

Chief38

 

[OldDragon30]

Thanks Chief. At this point, I'm really hoping it's my ammo. Otherwise, I've let a good gun be ruined.

 

[OFT II]

The cylinder should not be recessed. That could be what is causing your problem. It would cause the distance from firing pin to primer to be more than normal.

Ooops!!! I'm wrong as I'm thinking of a model 64.

 

[snubbyfan]

The 65-1 is a stainless steel, pinned and recessed, .357Magnum K frame.
The light primer strikes can be either too light of a mainspring, improperly seated primers or a loose tension screw.
Testing you ammo with a factory stock model 10 is a good idea.
I'd be interested in finding out what the problem turns out to be.

 

[snubbyfan]

By the way, welcome from the panhandle of West Virginia.

 

[Wee Hooker]

Try temporarily wedging a small piece of matchbook cover or cut& folded soda can skin between the mainspring tension screw tip and the main spring and re-tighten the screw. (Just 20-30 thousandths here goes a long way.)That will give the hammer more UMPH on the strike. If it fix's it, you know where your problem is. if not, you know where it isn't. Either way, it's a cheap fix.

 

[lebomm]

You might also try a spent primer cup without its anvil under that strain screw.

Larry

 

[OldDragon30]

Again, thanks to all.

If I get consistent detonation on the older Model 10's, my next step will be to use one of the techniques mentioned to increase tension on the mainspring. Either way, I'll report back to the group.

 

[OldDragon30]

More info...

I took the grips off and checked the mainspring tension screw. It was not all the way in. I was able to turn it about a half turn. I can't tell by feel of the hammer cock on SA or the DA trigger pull if that made a difference. But, given the information in the replies to this thread, it should have.

More to come...

 

[Sgt 127]

There are a couple ways to lighten the trigger pull weight. Turn the screw out half a turn to afull turn (easy fix, turn the screw in). Option 2, file down the screw so it has less tension (replace strain screw). Replace mainspring with lighter mainspring (replace with factory)

However, if he cut a coil or two off the trigger return spring, it may be too light to reliably return the trigger with a full weight mainspring. It will need to be replaced.

Lightening the trigger on a Smith is very easy. Making it lighter AND reliable is a balancing act. One your gunsmith needs to look into.

 

[hunter3705]

S&W revolvers are notorious for this. If you fire all single action, you will never experience it, it seems to only happen with double action fire. I have had this happen with a model 10-5, a model 17-4, a model 24-6, and a model 27-2. I'm sure you could solve it by installing a new mainspring and a new tension screw. My solution was to take a fired .22 shell case, grind it down on a bench grinder until all you were left with was the rim and little bit of the case walls. Back out the tension screw all the way and put the shell case over the tip of the tension screw, and then tighten it back up - all the way. This will solve the problem in most guns, and nearly solve it in most others. Interestingly, I was at the range today with a new-to-me circa 1976 model 34-1, and I had a few light strikes with it. At first I thought it was just the junk Winchester ammo, but then I had some CCI do it also. I've never had this problem with a J frame before. As I'm sure everyone knows, they have a coil mainspring, and no tension screw. I suppose the mainspring could just be tired, I'll probably replace it.

 

[OldDragon30]

Here's the latest...

I took one of my factory stock Model 10's to the range today and fired 36 rounds through it (all DA) from the same batch/recipe that produced 20% FTF on the Model 65. Zero problems. It's definitely the gun.

My plan is to put to use the good advice I have received on this forum. In the short run, I'm going to fabricate a shim to put under the tension screw using one of the methods described. And, eventually I'll replace both the mainspring and the tension screw. If the shim method works for me, "eventually" may be quite a while!

As before, I'll report back to the group on the results of the shim work. Thanks to all who have been so generous and gracious with their advice.

 

[M29since14]

...And, eventually I'll replace both the mainspring and the tension screw. If the shim method works for me, "eventually" may be quite a while!

Just be sure not to use this revolver for anything where function could be critical. If you might use it in some sort of emergency, it wouldn't be wise to rely on shims and such. It should be returned to factory specifications with a new mainspring and strain screw. Shimming might be OK for diagnosis, but I wouldn't want my life to depend on that kind of arrangement.

 

[OldDragon30]

I completely agree. I made the decision that this gun would not be a personal defense candidate when I had the original modifications done.

 

[OldDragon30]

New update...

I shimmed the Model 65 using a piece of thin aluminum doubled over between the tension screw and the mainspring. Then tightened down the tension screw as far as it would go.

I took the the gun to the range today and fired 24 rounds through it with no failures. To remind, two weeks ago the FTF rate was 1 in 5. I believe the shim corrected the problem.

At some point in the future, I'll replace both the mainspring and the tension screw with factory standard parts. Thanks to all for the help and advice.

 

[kaaskop49]

Yes, go with a formal fix ASAP. Some very savvy folks on this posting! I had a similar problem with a brand new Pro Series 686 not igniting primers on Armscor .357 ammo. When I was changing grips, I found the strain screw not fully tightened. Done, and no more misfires. By the way, the strain screw came from the factory like this.
Must be careful with used guns. Too many folks talented in other areas think they're gunsmiths and perform alterations not visible to the naked eye. And when they sell the gun, they do not mention these... Caveat emptor.