I have found the same thing with the syphon feed type sand blasters, the pickup tube clogs up a lot, have cleaned out the burrs inside the gun giving better suction, made sure the sand is really dry (even plugged up with glass beads. have even used an extra air line mounted close to the pickup tube to stop some of the clogging problems, but now i use the little one for small parts only. I have a pressure feed unit that hold 150lbs of sand and have used up to a 1/4 tip on it running 90lbs in the tank, but am using a diesel air compressor ment for running jackhammers with 210CFM air quanity is not an issue. I blasted the frame and supension parts over two days and painted using over 1000lbs of sand, backyard looked like a beach
