At the 500 yard line, the gas cylinder on my M14 would build up with carbon rendering the rifle useless. Whenever I fired a round, you could see dirt kick up in front of me. My Drill Instructor saw what was happening and fired the rifle himself. His solution was to clean out the carbon after each round. He said that if you were in combat that's what you would have to do or die trying. Not only was I under time restraints to qualify, now I had to clean the gas cylinder everey time I fired a round. To make matters worse, there was fog drifting across the target. In spite of the problems that I had to deal with, I became an expert that day. Thank God, I didn't have to take that rifle into combat. When I went to Sea Duty, I was issued an M1. What a relief. Instead of a gas cylinder, there was a spring. Front and rear sights were the same. Kept my Expert Badge.