I contacted MagTech and they have NO data for loading the brass shotshells.
So....I struck off on my own and used black powder.
Jest fer grins :-D an' gigles I used 11 gauge o.p. wads, and .5" thick felt lubed wads over 90 grains of Scheutzen 2fg and made mylar shot wraps, used modern 12 bore shot cups and so forth.
Got a very small chance to rip of a couple of relaods before it got too dark to see,
I loaded 13 # 1 buck pellets and at 45 yards put all 13 inside a 30" circle from an Chinese singleshot 'barn gun' with 30" full choke.
I did this twice.
I also have some loads with shotcups and buffer with #1 buck and a couple with 1 1/4 0z of copper 7.5 shot, no buffer.
The shotshells are easy to load and should last many firings.