Allen.. you never change the nozzle because you get a Carbide one. They are $50 or so for one nozzle, but I got mine about 15 years ago and its still just fine.
I had all of these problems before I went to the media I use now. Micro rust, or any anomalies come off at the same speed everything else does. I dont think this has as much to do with the media as it does the higher pressure? Bet its a combo of both.
http://devestechnet.com/Images/Restorations/1950B/D50b02015lg.jpgThat is my compressor setup. Its two EL Cheapo single stage 60 gallon compressors in tandem. I can run my blast cabinet all day with that setup and get no less than 100 psi. Less than that? You are waiting about 15 minutes for the compressor to build back to 100. Hope this helps! Holler if I can help!
