Pre Model 18, disassembled

[45Smashemflat]

Good evening,

I mentioned my recent purchase of a user grade K22 that was not super reliable. I got my good shop manual and figured I would do an inspection and complete tear down. Overall, other than bluing wear, the gun is mechanically sound. Cylinder gap is 0.002 (a 0.0025 enters the yoke side, but won’t pass through.). No yoke or cylinder end shake. Single action trigger breaks at 2.75 and double action is between 10-11 pounds.

In looking at the trigger pull thread, a see the references for measuring the mainspring weight on the N Frames. Might anyone have procedures/data for the K22?

I did find that the mainspring was not at all flat, so perhaps that is part of my misfire problem.

A few pics are attached. You can see how curved the spring is. This revolver is a ‘53-54 model, best I can tell. I was expecting the spring to be flat. Any insights or opinions would be appreciated. Still learning here!

 

[dfariswheel]

S&W mainsprings have to be curved.

The screw in front of the grip is NOT a trigger adjustment screw, it's a mainspring tensioning screw and has to be tightly screwed in.

The spring does look a little too curved, possibly someone installed an incorrect tension screw.

You can buy most S&W parts, including model-correct tension screws from Jack First Gun Parts........

Home - Jack First Inc.

 

[45Smashemflat]

Should have mentioned, the strain screw was appropriately bottomed out.

 

[Baxter6551]

I have no training in this but it looks to me like someone bent the spring trying to get a nice trigger pull. I would suggest a spring kit. I have used the Wilson Combat for all of mine except one Jerry Miculek spring kit which worked good also.

 

[austintexas]

Yep, Way back in the olden days, before Wolf springs, People sometime would bend a little curve in the hammer spring to lighten the trigger pull.
SWCA 892

 

[ken158]

Your spring has been altered at some time in its life. If you are getting light indent then I suspect you have found the problem.

 

[45Smashemflat]

Wilson’s site specifically says they do not recommend their springs for Rimfire. My plan was to go with Numrich. Does anyone have other recommendations?

 

[usedkid]

Jack First has them in stock…

 

[AzShooter]

Brownell's has stock S&W mainsprings. Numrich has them as well. I do a lot of business with Numrich and they are reliable and fast.

 

[CALREB]

45Smashemflat, PM me your address and I will mail you a couple good ones on Tuesday. I have to mail some other parts then, so no big deal. Your strain screw looks ok to me. Bob

 

[Protocall_Design]

You can simply straighten out the current spring to fix the problem. You don't want it totally straight, but with about half of the current bend.

Flat refers to the cross sectional shape of the spring more than the longitudinal shape.

 

[stu1ritter]

The procedure for K,L and N frames is the same for weighing the mainspring, only the specs are different for the N frame. In the Notable Thread section under revolver trigger job questions, the second post contains the factory instructions and the specs for K & L frames in .38 and .357.

Stu

 

[2152hq]

The firing pin in the frame may be loaded up with fouling from 70 yrs of use.
It's not an area that is normally disassembled and cleaned out. It doesn't take much to slow the FP down and cause misfires.

Try some thin oil into the assembly, work the pin back and forth and then blast the hole out w/ compressed air. It usually gets the cavity and parts about as clean as it would by disassembly..and is good for a check to see if it's the problem.

Check the Firing Pin protrusion in the frame as well. Leave the hammer down and the trigger to the rear and hold it there.
Then hold the revolver sideways and up to the light and look at the FP protrusion thru the breech face.
It should nearly reach the cylinder face, but not quite. That to avoid the peening of the chamber rim recess.

If the FP tip has been shortened (maybe damaged/chipped in the past and then touched up back to a rounded end), it will be quite a bit shorter and noticable.
That would cause misfires especially with some of the ammo being sold these days.

The bowed kink in the Main Spring was a quite common 'improvement' done when working over the actions some yrs back.
One 'smith I worked with used to do them with the gun all assembled and just the grips removed.
Place the gun in a padded vise. Put a brass rod, sometimes a wooden dowel thru the grip frame under the mainspring in that upper spot where the necessary change was needed.
Then with a hand on each end of the rod/dowel he'd give healthy pull back and kink the mainspring into that shape in one quick movement.
Out of the vise ,,click, click, click...grips back on.
.."All Done you ----" he'd mutter

 

[45Smashemflat]

The procedure for K,L and N frames is the same for weighing the mainspring, only the specs are different for the N frame. In the Notable Thread section under revolver trigger job questions, the second post contains the factory instructions and the specs for K & L frames in .38 and .357.

Stu

Just clarifying, you maintain the trigger to the rear while attempting to lift the weight? That is how I read it, just wanted to make sure.

 

[Protocall_Design]

Just clarifying, you maintain the trigger to the rear while attempting to lift the weight? That is how I read it, just wanted to make sure.

Yes, correct.

 

[Mike SC Hunter]

Yep, Way back in the olden days, before Wolf springs, People sometime would bend a little curve in the hammer spring to lighten the trigger pull.
SWCA 892

And they would put a pencil into the V-Spring of a Colt Python and cock it. To create a bend to lighten the action/trigger pull.....Been there done that......Caused misfires.......Replaced with new V-spring.

 

[45Smashemflat]

Quick update…

Picked up a digital trigger pull gauge and made a jig so I could mount it to my bench. I took some initial measurements (in samples of 5) and found the following:

Single action -2.5
Mainspring weight -4.2

I swapped in a flat mainspring (thanks @calreb)
Single action -2.5
Mainspring weight -3.2

I found it odd that the mainspring weight went down, but I wonder if that’s a function of the “start” of spring movement. I did not measure the double action pull prior to swapping springs. But with the flat spring it measured 8.5.

Putting in a 12# rebound spring from Norwich, I measured the following:

Double action dropped to 7.7
Single action dropped to 2.2
Mainspring weight stayed at 3.2 BUT was very consistent. 5 samples all measured 3.2.

No range trip yet, hopefully later this week. I picked up some CCI to test and will also re-test with my original ammo.

This is my first time working in the guts of a S&W. Learning a lot. It’s nice to be able to measure the changes. Not sure I made a “difference” yet.

 

[Nightowl]

The last .22 I had with misfires, I put the spring in a vice with the fork out one side, and closed the vice. It did not take all the bend out, but enough the misfires went away!

 

[mojave30cal]

You can also get that part on Ebay. Get one for a K frame. I
bought a 38 M&P made in 1924 over the summer off of GB.
It had a home made main spring and didn't function properly.
I bought one off of Ebay and installed it. Worked perfectly.