While ML deer hunting in Michigan in late 70's I was using a T-C Hawken .50 with T/C maxi-balls. Sitting on a stump watching a trail, I kept hearing a faint whistling sound. Looking around, I couldn't locate the source. After shifting my rear around on the stump to check all directions, and moving my gun from one position to another, I decided to re-seat the maxi-ball. When I looked at the end of the barrel the maxi was sticking out of the end of the barrel. Tipping the barrel up caused the bullet to slide back toward the powder, causing a faint whistling as the air vented past the projectile. I was glad that a deer didn't show and persuade me to pull the trigger with the ball half way down the barrel. The rest of the day the barrel always pointed to the sky, and after that, patched round balls were my load of choice. (maybe all that moving around is why I never saw a deer?)