I recently installed the Wilson Kit in an older K Frame Model 64-2 and while I liked the Main Spring that came with the kit I thought the choices of Rebound Springs, 12, 13 & 14 lb.s' were a little on the light side.
My M64 had been fired some over the years so I didn't have much work to do to clean up the friction surfaces. Just a very light stoning followed by a quick buff with a Dremel Tool & Flitz.
Because I wanted a "safe" single action trigger pull I went with the 14 lb. rebound spring but still ended up under 3 lb's on the single action pull weight, which was too low for my tastes. The double action averaged 9 lb's 0.0 oz. with the 14 lb rebound spring.
After some range testing where I had no light primer strikes, even with CCI primers, I decided to get the single action weight up some so, last night, I installed a 15 lb. Wolff Rebound Spring, which brought the single action weight up to right around 3 lb's, still a little low for me, and the double action weight up to an average of 9 lb's 2.0 oz.
I popped the sideplate one more time and installed a Wolff 16 lb. rebound spring, which brought my single action weight up to about 3 lb's 4 oz's, or thereabouts, with a double action trigger pull weight of 9 lb's 6 oz's. This is where I'll be leaving it for the next round of reliabilty testing.
I went with the Wilson mainspring over the Wolff because I have heard of issues dealing with the relationship of the strain screw & the power rib channel on the Wolff spring. The area on the Wilson mainspring is flat, like the stock spring, where the strain screw applies tension to the spring.
It's been my experience that all guns react differently to springs, which depends on how the friction surfaces work together, so your mileage may vary......
