For what it's worth, I set my iPhone on slow-motion just after sundown and shot 7 rounds of Titegroup, 5.5 grains, 125 grain coated lead bullet, and only had one round that showed a slight flash. I will try Trail Boss next. But both those powders are fast burners. I also tried my Henry with 6 grains of Trail Boss and got good groups at 50 yards. Then tried 6 grains of Titegroup and again got good groups. I think I'm going to love this Henry.