Now, I don't have any yet, so as of now, unless I could buy some stuff quickly (I think I can, though I need to look up the state laws), I would be pretty much screwed, but it isn't uncommon to have thousands of rounds of ammunition, especially when you are shooting milsurp ammunition, since that frequently comes in batches of a thousand. Supply depots would be at wherever I am based at (someplace defendable in the middle of nowhere), and in whatever I am using for transportation. When your gun jams, you clear the jam, not all that difficult, it is one of the basic things to know how to do, and even the M4, known for a somewhat exaggerated unreliability, only jammed one in six hundred shots while in a heavy dust storm. That is twice what people carry around when they are expecting to be fighting, and a jam can be cleared in a few seconds. By the time I run out of cleaning materials, your axe blade would have been worn away completely. If it breaks? Well, that is somewhat broad, but in general, you retreat using your back up and go back to repair whatever needs repairing, though for parts to wear out on a good gun takes... upwards of 30,000 rounds, I would say, and that is on the low end. Stainless steel, aluminum, and polymer don't rust, wood warps somewhat, but only if you don't take care of it. You are reaching for stuff, aren't you? If it gets wet? All right, you don't have to explain, I understand you don't know what you are talking about. If it gets wet, you keep shooting, a gun isn't going to stop working because of a light drizzle.
Also, you aren't likely to run out of ammunition unless you are going out and picking fights, what you should be doing is going in and out, grabbing supplies and leaving, the only time you would be sitting there shooting at zombies would be when you are holding them off, buying time, or when there are just a few attacking wherever you are.
But what about you? What happens when someone slips and falls? What happens when an axe gets stuck in a zombie skull? What happens when someone else gets tired faster than you?
edit: Boro, who were you addressing that to, him or me?