Long-term SHTF rifle caliber choices Ping.
.308 and 22lr
5.45 x 39 ... or a well equipped .22lr with a wide assortment of ammo velocities. I like the 60 grain Aguila for in close and personal work out of shorter barrels ... that tumbling projectile makes nice ragged holes and would hurt like hell, especially with three or four in a tight grouping.
Why? - You can buy plenty of factory ammo now. You can find all the reloading supplies you need (you can't find re loadable cases for the 7.62x39 Russian, if you can they are expensive, you are limited to cheap steel cases that can not be reloaded). You can carry 1200 rounds on your person (try carrying 1200 7.62x51 rounds). ARs chambered in .223 are a accurate as any bolt gun. The .223 Remington is a deadly round (loaded with the right bullet-powder combo you can kill deer and 2 legged game just fine with it, the 22LR just does not cut it as a self defense round). You will be able to find parts and people to help you with it for years to come.
I think every able bodied citizen should own an AR.
You and everyone else that shoots should take up hand loading your own ammo. It will take the cost of your 280 Remington shells from $1.25 each down to 50 cents per round. Get a press, dies, digital powder scale, automated case prep center, case trimmer with electric motor (1K investment) and you will be able to reload your own ammo for the rest of your life.
This is the best advice posted so far on this thread.
You should have 2
.22LR and .308.
L