I have found I get better fill out in the smaller calibres/weights, ie. under 50gr with the mold (Alum) around 400-420f and lead at 750-770f. And also concur with Loren, don't bother casting until mold is up to to temp.At this stage I use a lyman ladle and when casting the pellets I tip the ladle and mold together for a pressure pour. Some others here use the same method while reporting great results too.
You don't need to lower the level in the pot. Simply use the pour adjustment screw. For complete sprue puddle, at the end of the pour, lower the mold relative to the spout at the very end of the pour. It will leave a small spru. You will want to shut off the pour a split second after lowering the mold form the spout. This will leave a nice, small puddle. However, you will want to leave a few large puddles from one end of the mold to the other from time to time to help keep the top plate, (Sprue plate) hot, as pressure casting doesn't allow the required heat to be maintained. Knife