The tower is a tall, skinny building made out of stone and is near about fifty foot tall and hollow in the middle. It has a tunnel dug under it that goes to the river so water can get in under the tower. At the top, is a hole in the floor with screen wire over the hole. They pour hot lead on the screen and depending on how big the holes in the screen are, balls of lead form and drop down the middle of the tower. It falls into the water which cushions it enough to keep it from getting a flat spot on one side and also finishes cooling it.
Somebody gets in the water and scoops out the new bullets.
The size of the ball has to be the same size as the inside of the gun barrel you shoot it from, or maybe just a mite smaller.