just put together a 7 inch ar pistol from psa. Ive built probably close to 2 dozen ars from there uppers and parts and this is the first problem child i had. I would run right. Wouldnt pick up a round and acted undergassed. My guess is the gas block wasnt put on correctly. I fooled with it trying differnt lowers and bolts for a couple hours to no avail. Thought about pulling the upper apart but that would void the warantee so i called them and asked for an rma to send it for repairs. the girl answering the phone said we dont fix them anymore. We just dont have the people to do it. She sent me an rma and said they would just send a new one.