The guys have already covered what I've read and discovered in my limited experience. Powder can make a big difference. Blue-dot is usually dirty. (and big flash out of pistol!!!!!) But the pressure behind the bullet can make a difference too. Too much and you can have alot of leading. Not enough and you've got left over residues from the powder. Cast bullets are fun 'cause they make finding that perfect load just a bit more tricky.