media blasting gun won't work with some media! why

It works with glass beads and regular sand. I bought some media called Kleen blast 30/60. It's black and much more coarse than glass. The gun won't pull it thru at all! Just a short blast and then nothing. I even tried gravity feeding and it barely flows. I've inspected the gun and doesn't appear to be anything wrong. Air pressure is about 100, same as always.

Sooo... Is it because it's a cheap harbor freight gun? Are more expensive guns a different design?

size of hole in gun big enough?

I've tried both largest and smallest tips. No difference.

I should also mention that I have disassembled the gun (several times) and the feed tube. Nothing is clogged or broken. the media is the only difference.

I would suspect moisture coming through the airline, or maybe damp blasting media. Although, I had one doing this to me and it turned out to be a pebble that would get wedged up inside the gun. I didn't find it straight away. Also could be a pebble in the hopper funnel.

On my blast cabinet, I found I needed different size holes in the media pickup tube. For glass bead the stock setup worked fine, but with a course media like walnut shell I needed a larger opening. I drilled some larger holes and have a simple plate I clamp over the pickup tube when using the smaller media.

As mentioned previously, make sure you have a moisture trap.

With a cabinet setup, never fill the hopper up. Put in just enough to cover the pickup tubes with about 2" of media.

It also allows you to refresh the worn down media quickly without making a mess.

i have been using my red plastic bottled black capped...black metal gun...gravity feed harbor frieght gun this week and it seems to get a log jam in the feed down pin hole a lot too(think hour glass not flowing)...i had to take the tank off and knock the sand wedged in the hole free a lot....i may bore the hole a little bigger in the feed /holding tank.....it does it more when the tank is filled to the capacity...and when it is getting empty it will free fall out of the gun tip if i point it down ..but it is only annoying and i got done what i needed (old 550 kerker header)...still i would dig a better gun

Try higher air pressure, When I get clogs, I quickly plug the gun tip with finger and let it back flush itself, usually works.
I use black beauty and aluminum oxide mix for my course.
I have an old "vacu-blast" cabinet, it's got to be 40 years old. Lot of duct tape on the inside hoses.

I fixed it. After very close study of the gun and some testing, I decided the crap design was simply not capable of flowing the coarse media. I did a bit of "porting" on the inside of the gun and it works great now.

Thanks for all the input.

As you discovered the feed hole is too small for that material. That type of blasting media is very angular and sharp. It will lock together and "bridge" the feed hole or tube, keeping any material from flowing. Higher pressure won't solve your issue, only a feed tube or hole large enough that the material can't brige. Good job figuring it out