paincave,
I know this list is on AR15.com
I have seen this before when I was looking into why these rifles are so popular, but do ALL these names on this list MAKE lowers, surely not. What I have heard is say Sabre makes them for Colt, Rock River, Double Star, Daly, whoever, and puts their mark on it. Armalite makes lowers for themselves and who know who. Just like say Amana makes freezers for Sears and puts their name on it.
Surely there are not that many tool and die places turning out that many units? If there are that many manufacturers then I doubt there would be a shortage even with a war going on, and a citizen demand. That list is more than the MANY different companies that made MI Garands during WWII .