I thought I did it smart. Took hours to cauk the living shit out of a harbor freight blast cabinet.  Still leaks everywhere.  I am bout to replace my fu with a $100 TP Tools Skat gun.  Do I need to start over with a better cabinet or take it apart and caulk it all over?  I have a very real vacuum line but still get Aluminum Oxide everywhere

Tape all the seams with Nashua (foil) tape.

All the vacuum in the world won't help if your input pressure is higher than the outflow rate - do you have a water trap and regulator installed at the cabinet? Turn your pressure down and see if that helps.

Turn your air pressure at the gun way down. You're over-pressurizing the blasting chamber, and you've likely sealed up everything that could help you equalize pressure. Kind of like shaking a can of pop, then opening it. The internal pressure has to go somewhere. What pressure are you running?

Think about it.

Good points.  I have a good central vac and also an inlet to pull in air so the vac can take it out.  We run polymer at 30, aluminum at 60 to 75 and steel barrels 80 to 90 psi.  We have not adjusted nozzles for CFM.  We might be running too much pressure and volume.  We have a number of step-downs from the compressor and have a regulator dedicated for blast cabinet.

The blast cabinet is spot welded sheet metal and media finds its way out of the smallest openings that I did not know we’re openings.

We are also using a pretty fine media: AlOx 120.

It is frustrating when we think we have caulked everything to be caulked.

I am about to bit the bullet with a Trinco 300 # box 36” wide.  But I see TP tools selling kit plans to make your own with ply wood, so not sure what the right answer is.  I know I am spending far too much time on a blast box

I only realized this myself after sealing all the leaks on a top loading tabletop cabinet and still getting a face full of media every time. I ended up putting a Dust Deputy on it, which did help, but was pretty short-sighted because the cabinet I had was to damn little to begin with.

Some projects are just like this.