Threaded wise, I would vote Autococker threaded detents. A detent that's commonly available at pretty much any paintball pro-shop.
Empire feedneck threading is ICD threading .810 i believe.
Also, look at availability. Ccm feednecks suck. Huge, no lever and cor what they
Think how or what will go onto it, with it and design it with a little forethought on the finished product. How will it look with an intelliframe or a