Until recently I had never owned or particularly liked the humpbacks and instead preferred the inclosed hammer models. I had a 640-0 for a short time and then purchased an M&P 340 that I had and carried for many years. I purchased a 649-2 a short time ago and much prefer shooting it to the M&P 340. I just carried it with me yesterday on an all day MC ride. I really like the increased heft of an all steel J frame.