Somewhat of a thought experiment:
I hold some firearm out with a muzzle velocity of, oh, let’s say 1000-2000 fps. Assuming the firearm is perfectly level and about 5 feet off the ground the bullet will hit the ground in about 0.56 seconds.
Once it stops accelerating after it exits the barrel, it starts slowing down as the result of drag, but how much at the time it hits the ground a half-second or so later? I suppose that temperature would have some bearing on the slowdown, too.