Well, normally with regular chicken eggs, mine are out within 12 hours of pip. Not the rule, just how it goes for me. Bantam eggs take a bigger break , so 16-18 hours would be normal for them. Pay attention to the chirping, if it has weakened, or sounds like it's in trouble. If so, I would step in, and only slowly peeling back a small bit of the shell. The membrane in the shell is a network of veins that are directly connected to the chick through the umbilical cord. It's possible and common to break one of these veins when peeling them out. If you see fresh blood at any time put it back. The chick hasn't absorbed the blood yet and it is not ready. Wait a while and try a bit more again. It is a slow process, but has to be to be done right. Also, no matter how much shell you are able to remove the chick has to be the one to push itself out. It is a horribly important step in the chicks development, and something it neeeds to do for itself. All that said, I would still give it a couple more hours, as long as it doesn't seem distressed. Good Luck!!