I went to the range this morning to shoot my "Safe Queen" Pre-lock S&W 629 Classic. The gun had only been test fired before, cleaned and was put away. What happened next scared the hell out of me ! The gun recently had a Wolf Spring Kit installed by my gunsmith and all seemed fine. The first two cylinder fulls worked great but on the fourth round of the next cylinder full the trigger pull felt VERY hard. The trigger was all the way back , the hammer at full cock with a live round in the chamber and everything was froze up ! I could not open the cylinder and started to panic. What do I do with a gun in such a dangerous condition I thought to myself. After a few minutes of trying to free it up I was able to safely lower the hammer. I opened the cylinder and inspected everything and all seemed normal. I proceeded to shoot another cylinder full with no problem. When I got home I called Wolf Springs and asked for their advice and the guy told me in 35 years of business he never heard of a situation like this. His advise as the gun had not really been broken it yet was to dry fire it a lot to smooth the action out but he doubted the spring change caused the issue. I did dry fire it with snap caps for 50 times or so and all seemed fine. Any thoughts as to what caused this would be appreciated. Thank you !