Will, with regards to the gattling gun, have you considered a different bolt system?
I was formerly an armourer in the RAAF, and I have worked extensively on the M61A1 20mm gattling cannons that are fitted to F-18's & most other fighters. They are a 6 barrel gun, that use 6 individual bolts, operating on a campath inside the main housing. The campath is elliptical, taking rounds from the belt feed at the back of the case, up to the front/top part to be fired, then back down to the bottom on the other side, if you get my drift. The bolts and barrels are on the same longitudinal plane, and the whole lot rotates together. Everything is gear driven so timing is not an issue.
Sorry if i'm telling you something that you already know, but I thought it would be simple to make a similar system operating on 3 barrels.
Anyways, keep up the good work dude, it's always interesting to watch the RJF team.