Answer:
The equation that will express this result os
h = 0 = vy t - 1/2 g t^2    so the net height traveled by the bullet is zero
vy t = 1/2 g t^2
vy = 1/2 g t
vy = 1/2 * 9.8 * t       you could use -9.8 to indicate vy and g are in different directions
tx = sx/ vx  = 46.4 / 471 = .0985 sec    time to travel up and down to original height
th = .0985 / 2 = .0493 sec        time to reach maximum height
vy = g ty = 9.8 * .0493 sec = .483 m/s    initial vertical speed
Sy = vy t - 1/2 g t^2 = .483 * .0493 - 1.2 9.8 (.0493^^2)
Sy = .0238 - 4.9 ( .0493)^2 = .0238 - .0119 = .0119 m
Height to which bullet will rise - if the gun is aimed at this height then in .0985 seconds the bullet will fall to zero height
Check:    .483 / 9.8 =  .0493   time to reach zero vertical speed
total travel time = 2 * .0493 = .0986 sec
471 * .0986 = 46.4 m   total distance traveled by bullet