I have AR platform rifles in .223 and .308, as well as suppressors to go with them. First question I have is will the rifle cycle with a subsonic round? Second question is what kind of loads to use? I read in a American Rifleman magazine a few years ago, where you could use something like 9 grains of a pistol powder to achieve this. But I don't remember which powder and if that was for a .223 or .308. Any recipes for a subsonic load in either of those calibers?