Why do some in our community carry WAR loads of ammo when in reality they need only one or two mags to help them get outta trouble, the rest of the ammo can be cached at home or around your AOO or in your vehicle. I admit to being baffled by the often confrontation approach to being armed by some folks. Most of us will if lucky have a member of family around to share dealing with an issue but many folks appear to think they are going into battle against the Mongol Hordes.
https://www.cheaperthandirt.com/cat.../semi-automatic/223-remington-and-556-nato.do
Personally I would go for a 9mm or 40 cal pistol and carbine combo, a 16 inch barrel on a carbine is highly effective, but not a war fighting round. Troops often carry about 250 rounds of 7.62 /308 or 400/500 of 223/ 5.56 if they are determined , fit and looking to fight a battle, they could carry 600 rounds of plus P pistol / carbine ammo if so minded.
Being ex Brit LI I like to travel and carry light so five or six mags of 5.56 was a full load in the knowledge I had fellow troops also carrying similar loads. But as a Civilian I would probably only carry between three or four mags of Carbine ammo ready for use. I would do my damndest to avoid a gun battle against hostiles if I was on my own or only had my son with me. And what sort of Geography do you intend to live in cos if its heavily forested many ammo sizes are wasted in woodland at anything over carbine / shotgun ranges.