I've been feeding 3/8" Cargill for years, and never really had an issue with the spinner causing the jams. The majority of the time it was at the bottom of the clear funnel just prior to the slinger. Having said that, I'm going back to 1/4" pellets because Cargill lost a major customer for the 3/8" pellets, and now they require a 2 ton minimum order to make a run. Skretting does have available 3/8" pellets, but it's a little rich for me at the volume I feed.
