I don't shoot skeet or trap so I've never reloaded shotshells. I only reload rifle and pistol. However, I've been thinking about reloading shotshells lately. I've started with reading. And therein lies the problem. The more I read, the more confusing this becomes. For instance, what's the deal with hulls? I notice Hodgdon lists by shell; 12GA, 2 2/3" Winchester compression formed AA and HS plastic shells. But how do you identify as shell as such? Secondly, the subject of bushings is pretty obscure as well. If you have a MEC press, for instance, the powder charges (in grams) often seem to fall in between bushing sizes. And so on. None of the books I have seem to shed any light on these matters.