Posted this in NFA section and got no responses so I am hoping on this thread it will hit a larger portion of the membership. I am considering getting an Adams Arms 7.5" PDW Upper, but was hoping to get some input from some of you SBR guys. I have a 10.5" SBR already and agree that this is an optimal barrel length. That being said, I want something shorter just for fun. I also don't want to here about the short gas uppers and all the issues people have had with them as this is a piston system. Does anyone have any experience with this particular upper or with 7.5" piston uppers in general? Are they reliable? What are the downsides to them other than the noise and the huge fireball when you shoot it?