Some times, when people have consistent malfunctions with their AR, the gas system takes the blame, when something else is amiss. For example, one guy at a range I was shooting at had his bolt carrier would not return forward after firing, so he had to pull the charging handle back again after every round. The bolt would stop at the same spot every time (while I was troubleshooting, I put some white out at the spot to verify). I changed magazines with him, changed ammo, and changed uppers to rule out the more obvious faults. After putting his lower on the bench next to mine, I noticed that his hammer was at a slight angle. I took the other peices of the FCG off, and just installed the hammer pin, and noticed that the holes in the receiver didn't line up, and the pin was at an ever so slight angle. This was binding the hammer a little, and causing it to wedge on the carrier during cycling. I came up with the idea to put a rubber insert in the trigger well spring to strengthen it, then put it back together, and his gun started cycling like it was suppose to. I told him that was only a temporary fix, that he needed to purchase another receiver. My point is, the firer needs to spend time with his gun and get to know it, like troops in the old days did. If you know your weapon and how the parts in it function, you will have less to go wrong with it, and when it does, less down time. Safe shooting everyone!!