I also hear that normal JHP rounds can clog up when someone has on a thick jacket... If this is true or not, I dont know I would not think it would slow the expansion of the HP out. But from what I hear the ball at the end keeps them uncloged... Yea... I would think some jacket would be easer to let the round expand than a hard plastic ball. But, I dont care much about ammo, so much as it goes boom and goes down range fast.