The confrontation might be as far away as 7m, but a man can charge 7 yds, from a standing start, in 2 seconds, and under lethal stress, 2 seconds is a VERY fast reload, even if you have the spare mag in hand when the timing starts. So a reload, except from behind cover, is not likely to help you. With the heel clip type of mag catch, you can still manage such a reload in 3-4 seconds, twice as fast as one can realistically expect to speedload a revolver. Furthermore, you can keep one roundchambered while you do it, with which to shoot anybody who tries to charge your position.