Interesting choice.
My origional choice was a handgun (I am a city dweller) and .22 is a good choice for ammo availabilty.
A .22 does not have stopping power. You have to go with headshots.
It's for survival hunting, not combat. If it comes down to combat, I would have to go with this here Bowie knife and various skulking and sneaking techniques. If successful following that I would have the usual assortment of GI tools and acessories available.