Yes, it is possible to swap gauges on a PW 800B reloader. The 800 series uses a Star Gear indexing system that allows for easy gauge changes by swapping out the tooling head. Once you install the tooling kit, it's set up and ready to go without any additional adjustments. I'm not sure why they gave you negqative answer.
I have a very nice 800B 12 gauge for sale $250. plus shipping (I'm guessing too much). I'm in Northern CA.