Sand is less toxic and gives better insulation than perlite.
Generally cheaper, too.
Don’t cook or breathe over galvanized pipes, either.
Ammo cans can also have lead content that isn’t fit for cooking. Simple discarded tin cans from food items like corn are cheaper and safer to use for building rocket stoves.
If you are welding a rocket stove for cooking, then you must use food safe welds.
The advanage of perlite over sand is two fold perlite is much less abbrasive and weights a lot less.