Thanks for entertaining these dumb questions. They are firearm related even though that is an unusual thing for threads on this forum lately ! What's the history of all the various sources of uppers and lowers that are advertised for that particular line of rifles ? Clearly there is a big market for these products. Seems like an odd thing. Maybe it is to allow you to manufacture your own without needing a special tax or violating some law or regulation ? I'm looking to get an understanding of the reasons folks do their own build. ?/ for the fun of it (the Heathkit factor) ?/ overall better value than buying (do complete rifles have some heavy tax embedded in the price?) /? better quality in particular important parts I built my own (and friends') desktop computers in the past for the fun / satisfaction factor but never, in the last five years anyway, built one that had a better value than one I could buy already made. The retail parts prices of the components always made for a more expensive unit.