I still think the best bet is to avoid people. I don't disagree with you on the need to be prepared to fight, I just see starvation being more likely to kill me than my fellow man if I'm trying to avoid them. If this still doesn't make sense to you then I reckon we'll just have to disagree.
I agree,
in the long term.
Problem is, you have to get through the short term to get to the long term. In the first bit of time after Disaster X, is when people will panic the most and be the most unpredictable. After things settle down a bit, you will be dealing with survivors and people who have learned to cope, there will be less fighting and more cooperating to survive. You can't remain a lone wolf indefinitely.
The problem with these one gun scenarios is that there is two missions which work best with two different toolsets.
Mission 1: Live long enough to start surviving and rebuilding.
Mission 2: Long term survival and rebuilding.
Mission 1 is best served by a fighting gun. IMO the Ak and FAL reign supreme here because they can, indeed, be carried in a tennis racket bag, skateboard bag, large duffel bag or one of the long, slender "tower" type backpacks that people like to use -- presuming you're using a folding stock model -- i.e. bags one would expect a refugee to have. This is important to urban dwellers walking out (walking should be a last resort, BTW, not a first resort) because their biggest threat won't be looters, but police an military who will perform a knee-jerk gun confiscation campaign. No matter what you carry, you won't outgun them, so fighting them is not an option.
Once clear you
may have to fight to get where you're going, whether you want to or not. I don't care how ninja-like you are, everyone can screw up, and on the other side of the coin, the bad guys can just get lucky.
Now for this phase, you really don't need a lot of ammo, and if you do, as a single person, or dragging a wife and kids along, you probably won't survive such a fight even if you had the ammo. Which brings up another point: if you have a wife and kids, it doesn't matter how good you are, they aren't.
There are several ways to discreetly carry such a weapon and enough ammo (I'd carry one magazine for the gun, and 4 spares -- not a lot of weight).
Mission #2: Long term survival, is better served by a good foraging gun. I like the idea of a .22Mag over, 20ga or 12ga under combo gun. .22 Mag doesn't deviate more than an inch from 0 to 100 yards with a 100 yard zero, making it much easier to hit with than a .22LR, and the ammo isn't much bigger, nor does it weigh much more. IMO a lot more utility for little extra weight and bulk. The shotgun, bigger game and/or birds.
The dilemma comes in of which to choose?
Do I want to take the fighting gun and risk running out of ammo when it comes to hunting (why aren't you trapping, snaring, and starting your own garden?), or do I want to take the hunting gun and possibly not live to get to the point of not needing a fighting weapon?
So, once again, I'll choose the gun most likely to get me to the long term survival phase alive, and depend on tools that can be made on the fly and are much more efficient and reliable means of food gathering to get my groceries.