Is my sandblaster working, or am I using the wrong media?

I bought a 40lb Maxus pressurized sandblaster for a small powder coating gig Im starting on the side. I got it all hooked up inside my blast cabinet and started with "medium" glass beads, looks like reaaallly fine beach sand. IT said set to 60psi max for the glass, so I did but its like there is not enough pressure or something, theres alot of volume coming out of the nozzle (smalest one that came with the kit), but it wont even remove light rust on an old wrench. Would stepping up to aluminum oxide make that much of a difference, or is there a bigger problem here? I was hoping that AO set at 100psi would take off just about anything I need. Is this my problem, or is somethine else not working right? Thanks!!!