This sounds more like a prepper situation than a bug-out. If you bug out, it's not likely you'll pack 4 barrels; one extra max is more likely.
At any rate, the .357 idea is a good one, especially if you have a handgun so chambered. The .221 would be nice, but brass, if available, ain't cheap unless you make it from .223 and it's probably better to just stick with the .223.
Also, don't neglect to look into chamber inserts. With the Contender, you can shoot .22 rimfires in an insert-equipped .223 barrel and pick from several .32 rounds to fire in your .30/30.
Come to think of it, a .32 Fed or H&R barrel would be a good small game caliber as well, cheap on powder and lead. Brass is not too bad either.
Interesting project.
