Interesting theory... but human kind have created so many ways to kill that it's not exactly easy to weed out the imperfect just by having an open fire season. To weed out the weak, you need to have them do something physically demanding. A guy in a wheelchair could carry around a gun and kill plenty of healthy, fit people that should be classified the "fittest".
Which goes to show you that "natural selection" has become irrelevant in our unnatural society. Physical strength is not crucial to survival. It isn't "natural selection" when a hard-working construction worker is permanently injured by a faulty Mexican-manufactured crane at a construction site.
Such a man could probably your heads off with his bare hands, before that faulty Mexican-manufactured crane took his entire leg off. How is that "natural selection" exactly..? An unnatural society caused his disadvantaged state through an outside force.
In the meantime, we don't have "natural selection" in America. Nor do we have survival of the fittest. We do however have survival of the FATTEST, thanks to greed and corruption. If we were in the wild state, where natural selection actually operated, most of you fat slobs would be dead and gone within a week.
We are no longer living in the wild state of nature... so there is no more reason to artificially emulate it either by killing people for no reason at all.