If using a ladle, leave it in place on top of the mold so the bullet can draw from the melt in the ladle. I turn the mold parallel to the floor, place the ladle nose on the sprue plate and roll the whole thing 90 degrees to fill the cavity. If using a bottom pour pot, keep the sprue plate against the nozzle and then pull away slightly to leave a little puddle on the sprue plate. The bullet shrinks and will pull some material in to fill the void if the gate is not already frozen. Hotter bullets shrink more but the mold needs enough heat so the sprue does not freeze prematurely. Pure lead shrinks more than alloy with the rate of shrink proportional to the type of alloy and percentage of lead in the melt. I cast long rifle bullets and these practices work for me.