At the range yesterday, a guy told me I should never shoot 357mag in my 640 because it will "loosen it." What exactly did he mean and why would it say .357 on the barrel if it couldn't handle it? Part of what I like about revolvers is they seem like they will be around for grandchildren to shoot one day (30-40 yrs down the road). Is it wise to only shoot 38+p in the 640 and .38 in the 642?

