Of all the stuff I have used, 100 weight alox (aluminum oxide) is the best for guns. Finer grits will not cover and break a 320 belt polish very quickly and I find coarser weights leave a finish that marks and scratches very easily. I found that 100 weight garnet and fracking sand works nice and cuts fast but breaks down far to quickly in blasting tanks. Crushed glass also breaks down very quickly and washes hole edges and sharp edges on receivers so bad I will never use it again in any weight. I experimented with metal beads about the size of #12 shot which offered no coverage of polishing marks and only greyed old bluing. I got nice frosted finishes out of #5 glass beads but I had to start with a #600 weight polish to get the beads to cover polish marks. I accidentally bought a bag of #10 glass beads once. I knew better, but I poured some in the tank and tried it and found the only thing it might be good for was blasting fuzzy, wuzzy, little caterpillars and lovey, scrummy, baby butterfly's off of ladies silk undies. I gave it to my neighbor the auto mechanic to clean aluminum carbs. I generally blast at about 80 PSI.
