I think a better situation for a survival gun would be a combo rifle in 223 over 20 Ga. or 12ga.
I have a 410 and have done a lot of wing shooting but you have to pick your shots with the little 410. In a survival situation you will need to take what ever game you come across.
For survival a 12 ga would allow you to shoot any and all shot shells including buck and slugs. I know there are slugs for the 410 but I would not use them on medium to big game, they are only 87.5 grains at 1200 FPS. Also any large shot pellet loads in 410 will not have enough pellets to really do the job on larger game at any range. besides the 410 is expensive. Any thing 12 can do 20 can do. I know that is going to start a whole new argument. But, 20ga works and will work for any of your wing shooting or small game. Will 12 do it better and cheaper in most cases, sure! but 20 will still do it all too with less weight.
The 223 is accurate, available, with a wide selection of bullets, and is the happy medium for both small and big game. With 60 grain NP bullets I would not hesitate to shoot a deer out to 150 yards. If you feel more comfortable with a 308 or 30-06 then go for it and extend your range for big game out to 200 yards or more.
You may just want to get better with you revolver and shoot bullets at snakes. Your not going to have time to change ammo in the gun from big game to snake shot and back again. No matter how hard I have tried I have not been able to out draw a deer with my 44 and snakes just grow out of the ground. I can see having the snake shot in the gun and a spare speed loader with bullets while out hiking or scouting, but hunting your going to use what you have for the main animal your after and not want to carry a gun store shelf worth of ammo with you.
I can see hiking or meat hunting with a combo gun with 5 to 7 rifle rounds and 25 shot shells. Maybe 5 of them are buck shot. They make flares for the 12ga and you could use them to signal. Just be careful not to set the place on fire like the two quail hunters that were lost in San Diego county two years ago when they got lost.