I agree, the MEC 600jr is a good press for .410.
I have a universal charge bar in mine as I found the bushings were difficult to get the powder charges close to the recipes. I did put a plug in the powder side to move the cavity closer to the center of the drop tube.
I use W296 in my .410.
Unlike metallic cartridges, you load shot shell exactly with the components in the recipes in the loading books. Hull, primer, wad, shot weight and powder charge.
The powder manufacturers have loading data and there are a couple shot shell reloading books out there.