While this is an interesting poll, I question the practicality of your premise. If the "SHTF", you won't be hunting for food unless you were doing so on your own propery. If you're using your BOB, that means you're on foot, moving and hiding, trying to survive. Hunting is generally incompabible with that.
Also, a rifle in your pack is worthless as a defensive weapon, because it won't be in your hands when you need it. Finally, there's little point in carrying a rifle in a pistol caliber, unless you absolutely can't shoot a pistol well. If you're going to carry a rifle, it ought to have the POWER of a rifle.
Now, if the premise is really "I want a rifle to put in a pack so I can shoot while hiking," then you might look into the Marlin Papoose take-down .22LR, or an AR-7 from Armalite, Charter Arms, or Henry Rifle. Or even a 10/22 with the aftermarket stock that allows you to remove the barrel easily.
-Troy