I've always wanted a spool gun for my MIG. I have a Lincoln 185 Square Wave TIG, but thought having a spool gun setup for my Millermatic 175 would be the way to go, especially for tacking tubing together. Afterwards, maybe TIG, but I can hardly wait to give it a go tomorrow.
I have the argon tank from my TIG, so that's available already. My next project "may" require a lot of aluminium welding.
A spool gun is the only way to go with wire welding. I tried with my MIG torch handle once before, but the wire kept bird nesting in the welder's drive rollers. Got a great deal off eBay, new, just a few cents short of $300 for a true Miller Spoolmate 100, not the China rip-offs.
If successful, I'll post some pictures of my testing.
Hope you all are staying safe and healthy during this pandemic!