I took my new-to-me S&W m66 to the range today. I could not wait to run some rounds through this gun. This is the first run one I had been talking about in other threads. I put the first six rounds in it, cocked the hammer back, lined up the sights, and squeezed the trigger..."click." I could not believe what had just happened so I pulled the trigger again..."BANG!" A couple more pulls..."BANG! BANG!" Another pull..."click." I unloaded the failed rounds and place them safely aside. I loaded it up again and had pretty much the same experience. I kept going and always ended up with one or two unfired rounds. I removed the rounds the first few times and then loaded them into my m649..."BANG! BANG! BANG!" They all went off without any problems. I continued shooting the m66 until I was just about out of ammo. I found that if I went around the world twice I could usually get all the rounds to fire. I was just heart broken. Then I noticed something. The strain screw appeared to be a little far out. I got out my screw driver and found it was a full three rotations out from being tight. I tightened it up and then reloaded the gun. I only had eight rounds left by this time. All eight fired like a dream. I am going to have to go back tomorrow and see if that was truly the problem. I am sure hoping it was.