I just got a .22lr conversion kit for my AR, and I think it would fit the bill. All you have to do is swap mags and bcg which will literally take 15 seconds tops and you can have either .223 or .22lr. If it were me, I would stick with .22lr for a survival gun for small game just for the noise factor. .22wmr has a hell of a crack, but .22lr standard velocities or subs are pretty quiet. As for larger game, I have killed 4 pigs and seen dozens of deer taken with a well placed .22lr. My grandpa even killed a 80lb pig at 70yds with a .22 short when we were squirrel hunting. The .22lr will kill larger game, but if you could carry a .223, that would be a different ballgame.