Ammo is currency. Ammo is the opportunity to resupply those whom are fighting by your side. Ammo is the ability to stock burried caches, drops, and safehouses with provisions for those on the move. Because once a nonlinear shooting war starts, the ability to purchase more ammo with ease, relative anonymity and affordability is over.
Nobody plans to carry 1000's of rounds on their person which is why the ability to get more from what one has available is crucial. I would hate to spoil your "entertainment" but those whom would prefer to not become a "zombie" when the music stops have been actively preparing to survive such a time.
Many people will die if war starts, and a bullet doesn't care how prepared you are, it either connects or it doesn't, but preparedness and mindset will help you survive all the other horrors of war until the moment the reaper catches up.
The statement "Buy more ammo" comes with the unspoken mandate of applying common sense and buying spare parts, food, med supplies, training regularly, developing a close group of ready and capable individuals and praying that those dark days can be held at bay, etc. But that takes a lot of time and effort to type so...
Buy more ammo.