I carry an extra mag not so much for the extra rounds but in case the one in the gun malfunctions and here's why. One day I was going to clean my 239 and ejected the mag. When I did, all the bullets, the spring and the follower all shot out of the top of the mag. I realize that had I needed the gun I would have been able to get at least one round off but what about the rest? Would the mag continue to feed? I don't know. A careful examination of that mag appears to reveal that the feed lips are just slightly deformed. I'm glad it happened at home and not on the street.