I see a "Survival" Rifle having 2 roles. Foraging and Defense. 22's have the advantage of light, compact ammo that a few thousand of would be packable but would be iffy for stopping power.
9mm ups the Anty on stopping power with the benefit of potential resupply off of the people you would be defending against. The same with 5.56. Of course the government is probably choosing to go with a whole new caliber to make that less of an issue for THEM. While shotguns are versatile the size and weight of the ammo is far from portable. If they can displace people they can separate them from anything they can't carry. No matter how well dug in and supplied you are if they can contaminate an area they can rapidly displace everyone with the clothes on their backs. We have so much to look forward to!!!