In what way do you not agree a (hand)gun's lethality/firepower or capacity to kill or wound is not directly related to its magazines capacity(and caliber)?
With a derringer one can't kill many people, even if its was .50 cal. A Glock 18 with a drum magazine has the potential to injure or kill many more people.
And one-man clearing of rooms can of course be done, but you need to live long enough to clear a room. If there is one armed and alert person in a room, and you enter alone, clearing the wrong side first chances aren't in your favor. I would only undertake such a risky move if I knew family was in immediate danger, and there won't be any form of back up or other tactical advantage.
Obviously you're allowed to respectfully disagree with me, but for the sake of discussion it would be nicer if you could support your opinion with 'facts' or reasoning.
So please feel free to disagree with me some more, and reply to my question.