I said I'd give my opinion after giving folks a shot. For me, the survival AMMO selection comes before the picking the survival rifle. I have a list of requirements.
The ammo
must:
Be 100 % reliable every time.
Be widely available.
Be fairly inexpensive.
Be one shot knock down dead deadly at 10 feet and more than a mild annoyance at 100 yards.
Be deadly to both ALL food meat and every dangerous predator (including man) all the way up to brown bear of every type.
Be capable of being tailored to fit every shooter in my household. By this I mean, after they take the first shot, the shooter isn’t so hurt or scared they are still willing and comfortable enough to fire a second round.
I think that’s the definition of 12 gauge.
It’s available in 2 ¾, 3 and 3 ½ inch shells.
It’s available from 9 shot for the smallest bird all the way up to OOO buck shot and 1 ounce slugs.
Walmart sells 7s or 8s in 100 round boxes for under $40. I call that 100 meat meals in a box, or how to say “NO” 100 times. This ammo can be modified into wax slugs, or melt the lead and make 7/8th ounce slugs … or refill the hull with 6 - 00 buck pellets and make “cluster buck”, for a lo-recoil, good speed and ACCURATE 12 gauge surprise (check THIS out:
https://www.youtube.com/watch?v=q24gz_ZcYx4). You could make old fashioned cut shells, but I don‘t find them very accurate.
I know it’s heavy to carry, but I’d carry enough. I sure have enough stored.
As for the “installer”, or the gun to shoot it with, it can be almost ANY decently made reliable shotgun. Single shots are very good, 2 barrels are fine, I LOVE pumps, and semis are OK.
I prefer the shortest legal barrel length for good point-ability at home or in dense woods or brush.
I like a pair of sights on it with a ghost-ring on the rear end.
Add a sling, plastic stock and extended mag/tube as needed.
I have 2 Remington 870 pumps. One for shot, one with rifled barrel for deer slugs.
I don't much care that they don't float.