I would get a Ruger 10/22 Takedown.
7.62x39 is a dying breed, sorry folks, and I know I will get flamed. But as others said, it marginally "out performs" a 5.56.... even the Russians ditched it for a round mimicing a 5.56 NATO. Plus in a true STHF situation in the US... Chances are your friends, neighbors, in laws, local LEO's, and military units will be running around with and or dropping AR's and 5.56NATO ammo. Not to mention the ammo is a tab bit lighter, for packing it long hauls.
I suggest a 10/22 takedown for a few reasons. Everyone NEEDS a .22lr handgun and rifle IMHO. Nothing teaches fundamentals of shooting better, everyone can use one to practice. Two they are just plain fun. Three they are a damn near perfect little SHTF survival rifle with the supplied little case they come with. You can pack in in a pack, and carry your AR as a defensive gun, use the .22lr to hunt game. You can keep it in the discreet pack hidden in a car, because a true SHTF situation, you may not be able to make it back to your neatly organized gun safe. It is perfect for hunting game to survive on, and I don't care what anyone says, a .22lr semi auto rifle CAN be a viable defensive option.
Also if it is a TRUE social order collapse / pandemic, where survival outweights law of the land... and I am not condoning doing this under normal circumstances illegally, but a .22lr is pretty easy to make a makeshift suppressor for to hunt game discreetly, there's plenty of books and youtube videos on the matter.
Again... I AM NOT TELLING ANYONE TO GO MAKE ILLEGAL SUPRESSORS, but in a true SHTF social break down scenario... it is something to be considered.