I'v changed the Main spring in both my 617 and 625 and used 13# rebound sping in both also, what a difference! on my others 686's, 66's, 19's, 57's and 29's 27 & 28 all just the rebound springs feel almost identical to me and to others who tried them. I Didnt stone anything and alot of people told me not to they didnt need to be stoned!! alot said they had problems when gunsmiths other then S&W did it.(stoneing)