Ive been looking at load data and basic reading and I have noticed thst the hornady xtp bullets seem to have a shorter coal than most every bullet. the average coal for the 9mm is like 1.110 " - 1.120" . Why does hornady require you to seat their xtp deeper. Like my 9mm loads I did earlier this week said to have a coal of 1.120" but I used the xtp so I had to seat them deeper. why is that?