Well, alot in that spot. If you were talking about dropping from 33" to 30, almost nothing. But you are in a sweet spot from 18" to 26". I have seen 120fps drop going from 24 to 20. Depends on your load and powder also. Some slow powders are building pressure greatly at that point. Some fast powders have starting to drop pressures. Don't get me wrong, pressure is still building but not as fast.