I have a Ruger SP101 in 327 Magnum that I picked up used. I put a couple of hundred rounds through it prior to installing the Mcarbo spring kit with a 9.5lb Hammer Spring and 7.5lb Trigger Return Spring. I also added a Hammer shim to each side but didn’t require the trigger shims. After installation, dry fire with snap caps is perfect in both DA and SA. I took it to the range and put a couple of hundred rounds down range, no issue. Then, just today, while at the range shooting 32 H&R Magnum ammo, the hammer wouldn’t come all the way back when I tried to pull it for a single action shot. Some times, it would work fine, I could get 2-3 shots but then the same thing again. At home, I can dry fire it all day without issue with snap caps.
I did some very light polishing with only a low speed dremel with felt tipped bit installed and some Flitz polishing compound and only in the places that Mcarbo recommended, being very careful around the sear and other components, not really want to remove material. I’ve even done this same exact procedure with my SP101 in 357 and it works great.
Some of the guys on the Ruger Forum are recommending going back to the stock springs and especially suspect the trigger return spring. However, I love the trigger pull and don’t want to go back to the stock springs unless I have to.
Thanks in advance!