My personal thoughts are there is no perfect answer. 15-22 is a good dual purpose weapon in this scenario because it can be used for zombie killing and small game hunting(i have seen deer taken down with a .22lr).

I have carried a combat load of 5.56 and would say for a long lasting answer it would be hard to carry the hundreds of rounds needed for long term survival.

Me and the wife both have SIGs for personal defense but even carring a large amount of ammo would be hard. ( i have a P220 and she has a P239 in 9mm)

My neighbors and i talked about this last night and can to the conclusion tha a 5.56 or 9mm would be great because of the ammo available at ghost military bases.

I would have my .22 with me no matter what!!

My thoughts