In the immediate aftermath of a serious Mad Max level disaster (asteroid, megavolcano, nuclear war, etc), sure. Having supplies on hand to last from 2 weeks to a month to ride out the short term disruption of a disaster is just smart.

A few weeks out? You're going to have a market where gold is going to be the easy baseline, because doing 100% barter is a pain in the ass. Hence the emergence of trading shiny bits of metal as a proxy for wheat and goats eons ago. The natural properties of the metal happen to be really good for this - it's easily cut/worked, impervious to all but the most intentional chemical attack, difficult to counterfeit, easy to assay, and rare.

What's a case of 5.56 worth now, like around $1000? And it weighs like what, 15lb?

That's probably the most value-dense utility thing people are hoarding. Preserved food is mostly either water or air so you're looking at a pallet of food being worth maybe 2-4 cases of 5.56. Fuel is inconvenient and a bit dangerous to handle as a commodity so we'll consider any gas/diesel/oil/LP to be out of the picture as a bartering item.

Now consider gold, absent of any government interference in its market, has held pretty much the same purchasing power for millennia, and a 1oz bar of it will almost certainly be worth around a case or two of ammo or pallet of preserved food. This is just basic emergent markets, it's what people naturally do when left to their own devices (aka "a free market").

In the immediate aftermath of a serious Mad Max level disaster (asteroid, megavolcano, nuclear war, etc), sure. Having supplies on hand to last from 2 weeks to a month to ride out the short term disruption of a disaster is just smart.

A few weeks out? You're going to have a market where gold is going to be the easy baseline, because doing 100% barter is a pain in the ass. Hence the emergence of trading shiny bits of metal as a proxy for wheat and goats eons ago. The natural properties of the metal happen to be really good for this - it's easily cut/worked, impervious to all but the most intentional chemical attack, difficult to counterfeit, easy to assay, and rare.