I have 629-1 that I purchased a few years back, unfired in the box. I have shot it only in double action up until today. When trying to fire in single action, I begin to put a slight amount of pressure on the trigger and the trigger comes forward and the hammer falls, but not with enough force to fire the round. It also makes a different noise. The only way I have found around this is to slap the trigger a bit. I tried to get some of my other N frame Smiths (.357s and a .41) to have the same malfunction, and I was unable to get the same malfunction. I made sure the side plate screws and strain screw were all tight. Is this a problem with me or the revolver?