Without bearing the scorn of those repliers before me, statistics (and yes that is all they are and do not mean anything if you are the outlier) indicate that well over 90%, and probably closer to 99% than 90%, of all firearm discharges for use in self defense do not amount to more than 3-5 shots fired--well within the capacity of whatever firearm you are carrying. The likelihood of a "jam" with a semi is more probable than some kind of long-lasting "shootout" requiring anything more than those 5 initial cartridges. The statement is correct--the statement is NOT saying that magazines should not be carried if that gives you the confidence of more cartridges--it is merely stating the facts surrounding the use of a spare mag and when it ends up being used the majority of the time.