Please be aware that many of the WILSON Spring Kits #178 for the S&W K/L/N revolvers has a main spring that has multiply bends at the end that attaches to the hammer which make it 1/8 inch short. I received my kit from BROWNELLS and discovered this while doing a tune up on my L Frame Carry Comp. While testing the spring weight and dry firing the main spring fingers at the top of the main spring jumped off the pins on the hammer. I called WILSON and spoke with one of their gunsmiths who advised me that they were aware of this problem (spring too short)and it was caused by the manufacturer who supplied the springs to WILSON.
A customer representative who I spoke with advised that they did not know when they would get the correct springs and were advising anyone who purchased a kit with these incorrect springs to either return them or place them in a vise and straighten them to remove the 2 bends to lengthen the spring to the correct length.

WELCOME TO THE FORUM.

And thx for your contribution and advisement.

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Jim
S&WCA #819

Can you show us a picture of the spring you have?

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protocalldesign.com

So I have a set on hand...
This a good one or bad one?

Judging by the OP's comments, I'd say that was a bad one.

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John 3:16
WAR EAGLE!

As you have probably noticed, the Wilson mainspring is slightly shorter and has a different arch at the top. If you match this arch by bending your factory spring( I use a pair of visegrips) only at the top, you will have a nicely tuned mainspring. Save the Wilson spring for a template. This trick gives a reliable double action pull that is superior to those Wolff power rib springs. The magic is in the bend at the top. First that I have heard about the hooks jumping off the hammer stirrup. If Wilson admits to a problem, there certainly must have been a few complaints.

The shorter Wilson spring takes advantage of a little known tuning trick in the S&W flat spring guns. I figured this out on my own, I don't know if anyone else has done it or not. With the regular spring, the stirrup is up and back at about a 45 degree angle. This also allows you to run a lighter rebound spring because the hammer is not pushing down on the rebound slide as hard. If you radius and polish the mating corners of the rebound slide and hammer, you can have a very light DA with a snappy trigger return.

Edited to add pictures.

My version is to bend the mainspring into an S shape. The bottom of the S is toward the strain screw, the top is toward the backstrap. The only reason for that is to shorten it enough to get the stirrup horizontal. If you get it right, it works really well. The S bend sometimes takes a bit of tweaking to get it to work right.


This pic is comparing the customized spring to the original. Note the large radius bends. Second pic with the arrows shows the corners to radius and polish for best rebound return and angle of the stirrup.


The red line shows the stirrup in horizontal position. You will need to check for clearance on single action and make adjustments if there is interference of the spring and rebound slide.

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protocalldesign.com

Protocall Design, could we see a photo of one of your main springs please?
thanks,

Stu