Bullets drop like a rainbow because of time of flight. Provided they fly far enough, all bullets eventually drop like a rainbow REGARDLESS OF VELOCITY because acceleration due to gravity increases with the square of the time of flight.
g = G*M/R^2
Correct.
And if you dead-drop a bullet from precisely 6ft, it will hit the ground at the same time as a bullet shot at 3,000fps perfectly parallel to flat ground.
So velocity determines HOW FAR the bullet traveled before it dropped that 6ft.
The Ballistic Coefficient of the bullet determines how fast it loses velocity.
The “drop speed” cannot continuously accelerate as there is a finite speed for falling objects. Somebody dropped something off Pisa to prove that.
Unless you want to compute curvature and rotation of the earth for that extra millimeter over 10,000 meters.
Or so.