I tried to gain input on why Brenneke slugs perform like they do,what characteristics made them perform so well and pretty much drew a blank. So, I'm going to go ahead and see what I can cobble together. Comparing 20 ga. Brenneke shell and slug dimensions and a mod. choked 20 ga. barrel, with a mod. barreled 28 ga. and the available commercial products and their dimensions, I can see a couple of possibilities. One is to simply go with a .54 cal. sabot and a .50 or a .45 cal bullet . I don't expect much from that combo. next would be a .50 cal lead bullet of solid ,hollowed or thin skirted with an attached wad of felt or plastic. Has anyone gone up that road? Ken