I shoot triple seven pellets out of My omega, and have never had a misfire, or hangfire(knocks on wood). My Dad has an encore, and uses them also never had a misfire/hangfire. My Grandpa has a remington 700 ML, and His will missfire with the pellets, and hangfire almost every time. He's even did the 209 conversion on it. What We think it is, is His breech plug has about a half inch recessed spot in it where the pellets won't go down in. The T/C don't have that. They are flat on the end. So its less distance for the spark to go. Maybe Your sons gun is like that. I don't know if You can get different style breech plug or not, but that might solve Your problem.