Weight should never be a concern with staying alive, there isn't a swinging dick on here that hasn't begged, connived, pleaded, hoodwinked his way into gladly hoisting a 120lb woman up in the shower and hammering himself stupid! and will every damn chance he gets.
Carrying extra ammo could be the difference in getting to do that again, not to mention being alive to watch out for that woman and kids for the remainder of your life....
Jerry, I never thought of it that way, but that's a right smart way of putting it.
Anyways, I always carry at least one spare mag/speedstrip for any single-stack or revolver. A Glock can usually stay fed on what's in the magazine, or to fight my way back to the other magazines I have stashed in the truck/backpack.
