I entrusted my two favorite revolvers -- my S&W 625JM and 627PC to a highly respected local gunsmith for a trigger smoothing job and insertion of Wilson Combat Mainspring. He judged that the stock return springs were perfect and did not recommend changing them. He tested them with CCI primers (the hardest) and reports 100% tested reliability, so fingers crossed -- one of my requests was that the guns be reliable with all primers, not just softer Federal-type loads. Now if our local range will open I can range test them myself!!