It was so nice many years ago. Right after I got out of the Corps, I could get ammo cans of any size from my friends on base in Yuma.
A few years later, all my friends had moved on, gotten out, whatever, so THAT source dried up. Now, commercial sources are all that's left.
Ammo cans are great. If you want, you can drill them, and into the bed, and bolt them down, or just strap them tightly in place. Either way, they're still a great storage option, to me.
Pat☺

 

Ammo cans are great for a lot of things. They're rugged, their water tight, their portable. They don't fit everything though.

I made a battery box with a display and integrated charge controller for my HF radio out of a narrow ammo can. Works great for that.