My son recently picked up a decent K-22 of approximately 1946 or 47 vintage, lots of holster wear but mechanically good, with the exception of a tiny bit of cylinder end shake. I didn't get a chance to check it out before he bought it.

It's having an occasional misfire with multiple ammo types and brands (even the match stuff). The mainspring looks to be original as does the screw. I've tried to tighten the mainspring screw but it appears to be down tight. The firing pin is protruding well enough seems a little loose in the bushing.

I'm hesitant to use Power end shake washers so am asking for advice as to the best method to correct.

You may need to remove the sideplate and thoroughly clean and lube it. How does the area where the hammer and pin fall into appear? Is there built up crud there? Is the cylinder timing correctly as it rotates?
Heavy dried up grease at hammer pivot may slow the hammer fall enough to cause light strikes.

One of the first things we teach new shooters in our clubs revolver league is to make sure the ammo is pressed tightly into the chamber. Weather rim fire or center fire there can be build up in the chamber and the round will not seat properly. When the firing pin first hits the round it merely seats it into the chamber because there isn't enough resistance to set the primer off. If it still doesn't go off on the second hit then you need to look into other causes of the misfire.
Just a thought;
Mike

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Mike
S&WCA #2470

The masterpiece I received from my uncle and was doing the same thing you described. A trip to the plant cured the problem. Excellent customer service. It’s as good as new

All of the suggestions that bigmoose provides make sense and should be checked. Excessive endshake can result in misfires. The best remedy for endshake is either to stretch the yoke tube (gunsmith) or install proper thickness cylinder shim bearings; either of which provides the same end result. I have used the shim bearings on several occasions and they work very well. One thing to note is to also check for yoke endplay with the cylinder removed and yoke in place. Correct yoke end play first with yoke bearing, then address cylinder endshake with cylinder bearing.

I would for sure start out with a thorough cleaning, especially with a gun that old where you don’t know it’s history. That would include removing the strain screw and cleaning its pocket as well as the screw itself. Cleaning may not solve the problem but that’s where you need to start. I also check YouTube for any helpful videos.

How do the firing pin marks on all the cases look? Are they uniform and "normal"?

They look consistent.

The endshake shims work very well and I prefer them to stretching the yoke. The shims are hardened steel and provide a perfectly smooth hard surface for the cylinder to run on. .If that and a good cleaning doesn't cure it possibly a new tension screw. Some people (me) shorten the screw. But, I never leave one close to the edge of fire or misfire.

Yes we always check the seating. The chambers are nice and clean with no build up at the leade to keep them from seating properly.

I’ve removed the side plate and cleaned all the parts, the firing pin area looks nice and clean. Timing is perfect, the hammer fall feels a bit light.

My suspicion is cylinder endshake being the cause, there is no yoke end play (one of the first things I check on a older S&W). I’ll try the Power shims.

There is a possibility of a shortened screw, but finding a correct one is not easy for a pre number 5 screw. I have the yoke stretching tool but don’t want to use it on a K-22 this old. The shims will be my first avenue.

If the hammer strike force is unusually light, the mainspring strain screw may have been shortened. Buying a new one for comparison, or putting a spent primer on the old one and re-trying it at the range may help.

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Alan
SWCA 2023, SWHF 220

Geno44 hit on a problem I had with my 34-1. I had misfires on all kinds of different ammo but the marks were consistent. I have since shot 2 bricks of Federal with not a single misfire. It was the ammo.

My M17 had a similar problem with misfires. It had a broken firing pin. I quick and easy repair.

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Dave
Regulators mount up!

Re post #14, an expended small primer with anvil removed gives just a bit more "oomph" to the hammer fall. I know it's a Rube Goldberg solution, but it works. Absent a new mainspring or strain screw.

There are other ways to accomplish the result but this one is pretty easy and reversible.

If the hammer fall feels a bit light, this is likely the source of the problem. Rimfire rounds need a solid strike, and generally require a bit more mainspring tension than centerfire rounds.

I will second the suggestion to try a using the body of a spent primer as a shim on the end of the strain screw. There is a good chance it will resolve the issue.

I would also like to know the weight of the double action trigger pull. The pull weight gives a good approximation of the mainspring tension, so it provides an important clue about what is going on. If the pull weight is much below 10 lb on a rimfire, then that is suspect. If the trigger pull is already around 12 lb, then there likely is some other problem. Of course these numbers are not absolutes, but getting good measurements is still helpful.