I did the same thing a couple weeks ago with the Black Diamond. The media is too large to fit through the ceramic tip on mine. I have not had time to look for a larger nozzle tip, but I would think one would be available. The media was not damp/wet, it is just as you have said. It gets a large piece jammed and the whole thing backs up. I used 50 LBS of aluminum oxide through it the week prior to the Black Diamond and it worked great, but way too expensive @ $40.00 for 50 LBS. The Black Diamond was $7.95 for 50 LBS. Maybe I got what I paid for?
