I have shot the Magtech brass a lot. The only issue I have had is the slightly smaller rim, sometimes drops behind the loose fitting extractor on my hammer gun.
I also use large pistol primers, equal volumes of shot and powder, with cushion and nitro wads ajdusted to keep the over shot wad a 1/4" or less from the top. I seal it with white glue.
Since I shoot skeet, I do not know how the white glue would hold up under rough handling in the field or a wet duck blind.
There seems to be more blow back than with plastic shells and as mentioned, black powder required much more clean up. I usually deprime then washed the shells out with soapy water and a small nylon bottle brush. If I want them shiny again its SOS pad time.
Having started with muzzle loading shotguns, deassembly and soap and water gun cleanings are old hat. It is the price you pay to enjoy the sight, sound, feel and smell of black powder.
Good Luck
RPr