If serious hits, one is not going to have the luxury of a gunsmith on the corner, or being able to have the little brown truck bring them parts.
Less is More.
Simple is Good.
To reiterate what others have shared.
Plus what is proven to have worked...
-Single shot .22 and I like the option of being able to use .22 short, long and long rifle.
-Remington Nylon 66 and I suggest the butt fed model .
-Remington Speedmaster , (semi-auto) which will take short, long, long rifle
-Remington Fieldmaster , (pump) which will shoot S,L,LR
-Marlin 60
-Browning Auto .22
-Winchester 9422
-Marlin 39
Just what has been done numerous times before and still applies.
This is where a single shot, tube fed bolt, lever action and pump action rise above many other choices.
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Magazines are part of the gun, so if these get messed up, lost, one may end up with single shot.
Again, we don't know what the serious is, still magazines have to be considered.
Re
apoose.
The old ones were "less" ammo picky. The newer ones I have tried, are more picky about ammo.
Serious Situation, and getting ammo is to be difficult.
.22 rim-fire qmmumition is great Barter material, still it would be bad to have a gun picky about ammo and it not shoot it well, again leaving one with a single shot.
i.e. for some reason you lose .22 rim-fire ammunition, but still have wicks for oil lamps, and wicks for Zippo lighters and flints for Zippos, (other great barter items) and all the person has is standard pressure, or .22 shorts.
.22 short will take small game, or put down a nice size critter caught in a snare. Just ease up and put one near the back of the ear.
Though you might be best saving that round and using a sling shot with a rock instead.
Blending in another consideration.
Meaning something simple that allows one to travel more discreet, and in use, appears to be a simple gun, to put food on the table, or keep pests away.
Do not rule out a Youth, or Kids sized single shot either. A smaller person, such as a kid, has a right to a firearm too if matters get serious, and an adult can conceal and use one very effectively as well.
Go handle a Pink Cricket, Chipmunk , Marlin Youth, Henry Youth and see for yourself.
Sling it African carry, put your coat on, and go on about your business...