I mean would legally would all it take is an FFL? or a special FFL?

wonder if there would be any money in manufacturing actions.... to start at least,

although people probably would prefer complete rifles to just an action....?

perhaps manufacturing and selling to one of the big boys would make more sense? although I'm sure they don't want to pay a premium for anything.

Just curious/getting some ideas as to what it takes to build rifles. Maybe just call a custom rifle maker and ask them some questions.