I bought a m638 about a month ago and paid $360 to my FFL. At that time I had considered the m649 but just couldn't part with the well over $200 more in price. Well now I have a chance to do a straight across trade for a m640-3 (my gun also has the lock). The guy got it from his brother who kept it in his sock drawer (or wherever) for home defense. This guy has been using it as a daily carry for probably a year or so. Looks like it's been carried but mechanicaly it is excellent. He's looking for something lighter. My m638 is obviously lighter although there's not a lot of difference in overall size. Still small enough to slip into my coat pocket if I'm running to the bank at night. I like the idea of all stainless and .357. I hike and backpack a lot and would certainly feel more comfortable with the magnum. I live in a small(ish) somewhat isolated coastal town and really don't feel the need for a daily carrier. When I do carry it's usually in a coat pocket. The heavier gun would feel more noticable in that situation. Now that I have a chance to go up to the steel magnum I don't know if loosing the lighter 638 is really such a good idea. I guess i'm just looking for some feedback on the magnum and maybe some informed opinions on the trade.