I don't own an AR-15. I'm not a "gun person," whatever that means. I hardly ever shoot. And I never hunt.
But I'm nonetheless a big supporter of private gun ownership. In part, this is because I have a libertarian belief in civil liberties. In other words, my default assumption is that people should have freedom (the notion of "negative liberty"), whereas many folks on the left have a default assumption for that the state should determine what's allowed.
I also support private gun ownership because I want a safer society. Criminals and other bad people are less likely to engage in mayhem if they know potential victims can defend themselves. And I also think that there's a greater-than-zero chance that bad government policy eventually will lead to periodic breakdowns of civil society, in which case gun owners will be the last line of defense for law and order.