I have noticed that the gas plug, the slotted plug under the muzzle, comes loose. I noticed this after I went shooting a couple of times ago, but I had never checked it before. It was only held in by a few threads. I tightened it back up and went to the range again. I fired about 50 rounds through it and then took it home to clean. When I looked at the gas plug it was out a few turns. Is it normal for the gas plug to work it's way loose? Is there anything I can do or should I keep a screw driver with me to make sure it stays tight?