PSA has a ton of different affordable uppers for you to choose from. I'd check out their site and see what floats your boat. Yes, you could build one, but you'll need some tools getting started out, good punches, armorer's tool, torque wrench, vise block. I'd suggest a mid length gas system. Dont try moving your bolt between uppers, just get one with a bcg.
Last edited by killerv; 11/29/22.