I now have a full size, working copy of the core shaker. I tweaked the design last night based on the ideas of a friend (the sides or ‘fence’ is permanently attached to the top tray instead of the original design, which was a box that both trays sat in.
I tested it, and it works! There are still a few kinks to work out (the biggest one is that the cores are catching on the edges of the jackets). But at least I know I won’t be manually placing a core into each jacket when my final set of swaging does arrives!