Some of you may remember I built my own a few years earlier when the "idea" first came out.
It's fun. I have the Tac-Sol mini-shell adapter for it, but mainly I just shoot my "birdslugs" through it. The blasting-fodder load I use for my Saiga 12s to keep 20 round drum mag dumps reasonably priced.
Once or twice used Federal bulk pack cheapo shotshells, whatever trap wads are on sale, whatever scrap lead I can find, as long as it pours and casts it's good, because the 1oz Lee Key-Drive Foster slug I mold is only .69 caliber and rides in a standard shot wad, no bore contact or leading to worry about. And I load it over a 209 primer, and 17gr of 700x Hi-Skor powder.
So it's a slug, but only 1oz of mass moving with what would otherwise be a trap loading, and very low pressure, since a solid slug doesn't squeeze or "bean bag" down and out to the sides of the bore like #7.5 or 8 shot would.
Since I ordered a 14" Mossberg 590 barrel with the ghost ring rifle sights on it, it's a bit more tempting to use it in "face smasher" mode, but with the push-pull hold it's not really that hard to control if you're used to 12ga in general.