there is one feeder that is called the stright shooter that the feed is not exposed,so it will not mold.
Don't know if it will be what you need or not.
Just try putting corn in an automatic and it doesn't mold.the deer love it.fix you feed station for the pellets,only put a little at a time till they get to eating them good and then increase the amount.
I am not a hunter ; I am a whitetail population reduction specialest
remember keep your back to the sun, your knife sharp, and your powder dry.