The zombie apocalypse is obviously pure fiction...
Not exactly. It's a metaphor. Communicable diseases and social breakdown in cities are both perfectly real, as are the likely consequences of the dwellers therein attempting to escape. The walking dead part of that is essentially irrelevant, as the author does come around to conclude himself. And by the way, the mathematics of epidemics and migration are similar to the ones the author showed for floodplains, and just as scary.
So thats another canary in the coal mine for the tin foil hat right winger you have a class of people who are vehemently demanding confiscation of rifles in the public sphere, while some of them are secretly building underground fortresses in the private sphere.
Buy another box of ammo. Clearly.
Oh, yeah. The answer to "what do you need a rifle for?" is the same as to "what do you need a bunker for?" - it's "you don't need one at all, until you do." Make that several boxes.
Ammo cans. Ammo can-sized boxes.