Mcwoodduck has given you good advice and truthful advice, but be aware that the issue is not that plastic hull loads will be dangerous in even the thin Magtech brass hulls, but that they will be rather anaemic, especially given the issue with wads. You can still use plastic shot cups, but you need to get oversized nitro and felt cards to "stablize" the shot cup. You will then use oversize overshot cards fixed with waterglass or Duco cement. These types of loads will run lower pressures and consequently lower velocities if simply substituting plastic hull loads. There are smokeless loads that will work well. But you should indeed contact BPI and use data for brass hulls. I f you don't already have the Magtech shells, Rocky Mountain cartridge has better brass (the best there is) as well as a brass loading kit that, while not rocket science, will save time and effort. They will also have load data.
