Greetings and salutations,
Since the logistics of finding usuable ammo for their weapons was becoming a problem for the group I used to run, they got smart after generating a second or third character that using bows and arrows, swords, clubs, shotguns, and the martial arts was not a bad idea (especially after their encounter with some American/Polish/Soviet marauders that tore through them using just those items). Sometimes having the latest and greatest does not work towards one's advantage when everything around you has broken down. It would be great if the group could secure an ammo factory and supplies to produce the ammo they need, but that would be a huge hassle when other people learn that you can do such a thing. Some will set up a trade agreement, others will try to take it or whatever they can by force.
Besides, by the time the characters start campaigning, most units will have adopted a policy of firing their weapons only if they have too. The group had a few encouters where they turned their weapons on approaching groups but did not fire a shot or fired a shot burst from a machine gun. Amazing how people scatter and/or want to negotiate.