If you want to keep the same lower, try going to 7.62x39mm Russian.
C Products makes the magazines. The uppers, bolt carrier groups, etc can be found at www.model1sales.com
NRA Chief Range Safety Officer, Home Firearms Safety, Pistol and Rifle Instructor
"There are three classes of people: those who see, those who see when they are shown, those who do not see."
Leonardo da Vinci