How do you re-tension a mainspring?

[Pastprime]

The main spring in my K-22 has been bent incorrectly. There are shims between the strain screw and spring to create sufficient tension. Is there a procedure for re-shaping or re-tensioning it? I could just put it in a vise and bend it but I don't know what the original shape should be. I'd buy a new one but when I looked at Numrich, there were 4 or 5 offered for a K-22 and I have no idea which one is correct. Advice is always appreciated.

[Simmer down]

Have you checked Wolff springs?

[Pastprime]

I didn't think about them, but I'll check their website.
Thanks.

[199]

I'm not saying your spring isn't improperly bent, but:

At one time folks would shorten the strain screw to lighten the trigger pull. At a later point, someone would shim the shortened screw to increase the tension.

If that's the story here, you actually need a longer strain screw.

Granted, people did sometimes bend springs as well.

A photo of the spring would help.

[Mike McLellan]

If you're in doubt, replace it.

[murphydog]

If you e-mail Numrich with the SN of your gun, they should be able to tell you which part fits. Agree with replacing the mainspring...and the strain screw for good luck .

[Hapworth]

It's easier to replace -- they're cheap. Re-tensioning takes experience and a jig to apply pressure throughout the leaf spring rather than at a concentrated (and therefor weakening) point.

Then a specifically designed weight set to test the springs tension against and make certain it's to factory specs; then a trigger pull gauge to make certain it's also to factory specs in double and single action.

And if you're really thorough, a special case to hold a copper plug to drop the hammer on and measure the indent to make certain you're hammer's dropping with enough force to pop primers.

Or just get a factory replacement, or a Wolff if you like to tinker.

[steelslaver]

To properly reform a spring it should be heated to its critical temp around 1500f and the reformed to correct shape then tempered 850f for 2 hours. (normal spring steels, stainless requires higher temps)

To bend a spring you must move it beyond its elastic limit. This will weaken it somewhat. You can do it, but will never be as good as a properly done spring.

[4barrel]

I have a nos k frame spring. PM if still looking.

[H Richard]

There is very little difference, if any, on a K Frame mainspring over many years. Are you having light hits and miss-fires? If you order a Wolf, find out if it has the "rib" down the center. If so you will need a different strain screw, and they can't tell you how long, it is a trial and error fit.

[chief38]

They are so inexpensive I would just replace it. Even if it were "re-bent" I doubt the tension would be correct for long - but that would depend on how much you need to bend it back. I'd just replace it and be done with it.

[Neumann]

Smith .22 revolvers are notorious for heavy DA trigger pulls. The fundamental reason is that .22 cartridges are notoriously hard to ignite. There is/was a powerful, if misguided, incentive to lighten the trigger pull. It is misguided to the extent that .22 revolvers are nearly always used SA for target shooting and plinking.

If you are getting light strikes, it is advisable to replace both the mainspring and tension screw (which was often ground shorter to achieve a lighter pull). Don't be surprised if the DA trigger pull is on the order of 13#. (My pull gauge stops at 12# and I can't measure my M-17 no-dash DA, but the SA is 2.5#).

[gboling]

The one issue overlooked here is that new strain screws generally, if not always, require shortening to achieve the proper trigger pull weight. It requires a trigger pull scale and extreme patience. Having extra strain screws on hand after shortening a screw too much is always good for the blood pressure.

If you have no experience with this, contact S&W or a competent gun smith.

[Pastprime]

Always more to a job than I anticipate. Thanks for all of the excellent information and advice. I PM'ed "4barrel" and looking forward to putting an original back in.

The more I read about S&W hand guns from all of your posts here the more I appreciate the workmanship that went into the K-22 I have. Kind of makes me want to get another one, or two, or three, or .......

Hank

[gboling]

Originally Posted by Pastprime

Always more to a job than I anticipate. Thanks for all of the excellent information and advice. I PM'ed "4barrel" and looking forward to putting an original back in.

The more I read about S&W hand guns from all of your posts here the more I appreciate the workmanship that went into the K-22 I have. Kind of makes me want to get another one, or two, or three, or .......

Hank

You exude the symptoms of another addict. You simply cannot stop at just two or three.

[shawn mccarver]

Originally Posted by Pastprime

The main spring in my K-22 has been bent incorrectly. There are shims between the strain screw and spring to create sufficient tension. Is there a procedure for re-shaping or re-tensioning it? I could just put it in a vise and bend it but I don't know what the original shape should be. I'd buy a new one but when I looked at Numrich, there were 4 or 5 offered for a K-22 and I have no idea which one is correct. Advice is always appreciated.

You are better off to simply buy a new one, in my opinion. The parts people at Numrich should be able, with a phone call from you to give them the serial number, approximate date of manufacture, etc., to find the correct part number for you.

[Pastprime]

Originally Posted by gboling

You exude the symptoms of another addict. You simply cannot stop at just two or three.

Well, I am just recovering from selling most of my rim fire target rifles so the weakness is certainly there. Hopefully, I'll be able to keep the S&W urges to buy under control....hopefully...

BTW, "4barrel" made me a very fair price for a main spring which I accepted and should have a correctly shaped spring in next week.

[Nightowl]

A new spring is the best answer. While you are waiting, just put in a vice, lengthwise, with the hooks ourside the jaws, and clamp it straight. Unless it is bent so much that it breaks, you can't really hurt much and it might actually work for awhile. I have done that on a few with good luck. You don't have much to lose at this point. :-)