Hardin stoves were made in Hardin, MT awhile back. They are no longer in production, but I've heard they are a decent unit. There are a few out here in WY/MT. It would be great to see a few pics of your burner/retort etc.
I have had problems with my Prill stove smoking from the coal bin/auger before. I think it was caused by having too much combustion air. Once I closed the flapper some on the combustion air intake, it seemed to stop. It was a sign that I was sending too much heat up the chimney too.
If your combustion air is too strong, your probably sending alot more flyash up the chimney too. Once I turned my air down, I noticed dramatically less ash accumulating in my horizontal section of smokepipe, and my exterior cleanout tee stays much cleaner too. My ash volume dropped to about 1/3. My ash is not melting and clinkering some, but still gets broken up by the rotating ash ring and drops in the pan. Life is much better now.
I'm sure there is a way to adjust to coal feed rate, if you need to. You just need to get a smaller motor pulley (less feed rate) or larger motor pulley (higher feed rate). It may even be an adjustable pulley already. Or you can do the opposite on the gearbox.
My experience is that you have to do alot of playing with the coal feed rate, especially if you get coal from a different mine that the previous owner burnt. I don't think that's your problem with the auger smoking, just something else to think about.
Not sure what coal your using, bituminous or anthracite, but the previous Prill owner burnt sub-bituminous coal, and I'm burning bituminous, and I had to do alot of fiddling with air and feedrates to get things working right.
Good luck - post with your successes too.