Since its a survival gun that you actually depend on surviving with it has to be accurate, reliable, a effective caliber thats prevalant & cheap to shoot so you can have allot of ammo on hand.
You could fill in what your personal choice is for guns.
Robust, scoped, handy quiet and a repeater (had covey of ptarmagan sit till I got the 3'rd one before they flushed).
My personal choice's would be wittled down to the following#1 a Remington Nylon 66 #2 Remington 572 pump, #3Taurus 72 pump carbine,#4 Browning semiautomatic .22 (reliability), #5 Winchester 9422(reliability),#6 Ruger 10/22 (sights suck,mag release is a problem,mag's can be lost), #7 marlin 60 love them tube mags , a good 20ga pump shotgun(H&R or Mossberg) or a good double barrel .410 or 20ga as you can see Im a .22 guy and very lately am into shotguns.
Id suggest old calibers but you'd have to reload (218Bee,32-20,25-20,.22Hornet,.22 High power) when these calibers in ther day they were good rounds.
The Gun's Id suggest avoiding ................Are survival rifles especially the AR7 clones they are at best a handicap and when your survival is depending on takeing a shot with limited ammo, use the best you can afford! Why handicap yourself with a gun that's fragile, poorly sighted, and oft times inaccurate, survival useally means Hunting and Defending yer nest when its required, so get a good hunting gun, ther built for killing accurtely so pick one that your wicked accurate with especially running shots and shots in low light situations.
I dident mention the henry lever action's .22 because the front sight and barrel bands on some them are plastic and wouldent stand up to getting beat a little, if they did have all metal construction it would move it to #3 or 4