Maybe I'm oversimplifying it...
Gravity's effect/bullet drop on the bullet is linear as we all know...Newton...
Gravity accelerates stuff that falls. The distance fallen in ft = 1/2 * 32.2 * T^2 where T = seconds.
If the bullet doesn't slow down, you can expect 4X the drop at 200 yards as at 100 yards.
Exponential functions result in a curved path, like a bullet travels.
Linear functions result in a straight path, that's why we call them "linear".