I don't think that hunting or the aspects of target shooting that are disconnected from the use of guns against human beings really have much impact on the conflict over gun regulation.

The notion of sufficiency has to do with the probable (or inevitable) effects of something. So it doesn't map well onto thinking about the contingent effect of specific choices. While it's possible to have a system of ethics that's more about probable effects in aggregate than the contingent effects of specific choices, conservatives generally favor individualism over collectivism. Since the ethics of justifiable homicide are at the root of this conflict and the opposition to gun regulation is generally conservative, notions of sufficiency seem likely to miss the mark here.