wait, how do you manage .22LR in that?
also, from reading the specs, the circuit judge requires a choke to be "effective" with .410 shot, which much be removed when switching up to other types of ammo. that seems like it could be a pain, esp if you forget.
survival gun. well, how should that be defined? something to help you survive. doesn't have to be pretty, or 100% accurate, but it does have to be rugged, simple, and always work. to survive. not revel in 20 point elks, or take down any land animal, or for that matter, even large game. towards that end, a rugged .22LR or even .22WMR would be just fine, i should think. depending on your survival situation, you might not even NEED a gun. traps, snares, or even nothing but water for 5 days until you get out. longer? well, there's a certain point it's not survival, and then you make other plans (esp if say, everyone turned zombie ;>)
that said, i'd think a pistol of some kind, would be ideal. .22WMR pistol will knock a lot of meat off trees. so will .22LR. those henry survival rifles would be just lovely, i should think; or a pistol you can put a stock on. mmm.
a very small, bolt action .22LR probably would be super ideal. make it stainless or titanium, with a lot of polymer synthetic bits, and now we're talking.
the m6 is pretty dandy, i must say.