When you cock the hammer does it act normally until about 3/4 cocked and then suddenly get hard to finish? If so 2152hq sort of touches on the problem, but his explanation is flawed. If the strain screw is loosened too far, either deliberately of just from shooting, the mainspring straightens out and effectively becomes longer. The lenghtened spring then "stubs" under the arch of the hammer when cocking the gun. If you take the side plate off and watch closely when cocking the hammer you will see clearly what is happening. It has nothing to do with the spring striking the frame, the rebound slide hitting the spring, or anything else.


I notice that even after being told to tighten the strain screw, in today's post you don't mention even trying this! Why not? Humor us, tighten the screw and then tell us what happened! Or can't you believe such a simple thing could be the problem?


There are two other situations that can have the same effect/symptoms. First, the mainspring could have been shortened having the same effect as loosening the strain screw. Second is the mainspring may have been replaced with a Wolfe "Power Rib" spring. In this case the strain screw settles into the groove of the power rib with the same effect as the screw being short or loose. Either situation can be checked by putting a fired primer cup over the mainspring as 2152hq suggested. If this fixes the problem then replace the strain screw with one that is longer!


NOTE: The mainspring should have a very distinct arch when the strain screw is properly fit! If it appears nearly straight this is the problem. A photo of the gun with the stocks off would be very helpful in diagnosing your problem too!


NOTE 2: There are several common malfunctions of S&W revolvers which can be "fixed" by simply tightening the strain screw! This is the first thing to check. "Tightened" means the screw is bottomed out and can't be tightened further. This is how the S&W strain screw must be installed, it is not an adjustment!