I have two pounds of the mixed stainless media. The manufacture only
states that it is stainless but not which grade. I can only assume,
and I shouldn’t, that it is a type 304.
This stainless really shouldn’t ‘rust’. Although it can get
contaminated when used next to carbon steel.
When I recieved my shot it was rinsed after the first use and dried
on a paper towel. Next day rust was found on the towel. A magnet
found about 75 pieces of the shot were carbon steel. They somehow got
mixed in with the stainless.
I don’t use my tumbler very often so I always rinse and then dry the
shot for storage. I don’t know why they want you to store the shot
wet. I hope you find your problem.