That discussion came up a number of times previously. First, after a catastrophe like that, people are going to be stuck at their relative location. They're not going to go across the country very often. National groups become very regional. So whatever resources were in the area at the time this show is set becomes what they have. Right after there'd be a lot of fighting, ammo would be used up pretty quickly. Sure, there could be National Guard Depots with 1,000,000 rounds, but unless they are within a few days travel by horse then it's going to be out of reach for most people. Even if you do get there, you can only transport back with you what you can carry. Reloading would occur, sure, but primer caps would run out eventually and then you're at a point of having black powder and recovered lead. So you're at blackpowder guns. This show is 20 years after the show, it's not surprising that people would run out of manufactured ammo. There very well may be some people who still have modern weapons in the show, that was only a preview, and I can guarantee you they'd be people in power. But resources would become scarce and they wouldn't be that common.
