stiguy,
take it easy bro- you dont have to react as if i'm making fun of your mom or something. im just sharing what i know from my experience, which is my upper happened to work, but back in the day folks were reporting problems with those configurations. it seems that much of that came from simply cutting 20" barrels down and having a go. even today gas port sizes for same-length barrels vary from manufacturer to manufacturer, and they knew much less about this stuff back when the first 16"/rifle-length-gas-systems came out than they do now. as a comparison, i also mentioned that i've had ar's in more traditional configurations not work from the factory, be it 16", 14.5", 11.5" or 10.5", so i'm not singling out this configuration as condemned.
i'll say it again, but it seems like dpms's are running fine from the looks of it. i'm glad your system works great with certain ammo. i know that bruce's duty rifle works well. i hope revopop's project works out and want to hear about his success. lets all relax and help each other have guns that work.