Ammo Boxes give reserve ammo for your gun. The amount depends on the type. However, the Large Red Box only gives small brown box reserve now. That said, you must touch it multiple times to "fully restock your ammo". However, there are special Large Red Boxes that still exist that still give time x3 your Default Reserve.
Small Brown Box: Default reserve (How much you get when you spawn)
Small Green Box: x2 Default Reserve (Twice amount of spawn reserve)
Large Red Box(Normal): Default reserve, must be touched constently to fully restock.
Large Red Box(Special varient): x3 Default Reserve (Triple amount of spawn reserve)
It is best to reload before touching the box to get the maximum amount of ammo you can hold on that gun
If you touch a smaller ammo box that normally appears ingame, your ammo will be decreased to the default amount you spawn with
Like all buildables, it shows a strange menu for a "claymore" that does not exist in game.
It can go through walls.
Speedy thought best to put in muntio scripts for Stranded on earth. Personally, i would like it if the reserve maximum was higher. But meh. Sorry people, no moar buildable OP red boxes.