Clean the mold and make sure no oils are in the cavity. Smoke it. Make sure the mold gets up to temperature, this may require filling and tossing many, I use an old laboratory hot plate for warming up to about 400 F. Do not put the sprues back in the pot because it lowers the temperature. If all that fails, turn up the heat. If you don't have one, buy a lead thermometer, used to be like $30 for the Lyman digital. Go between 750 and 800 degrees (my Lee pot swings pretty big)
For powder coat... Make sure to clean the ammo with alcohol to remove any oils and make sure they are dry and a little warm, I use a heat gun for this. Use black Crosman air soft BBs to help generate static. Use container with a recycle #5. Shake, a lot. If none of that works, it might be your powder. Not all colors and brands work well in this method. Eastwood Cadillac Blue is my newest favorite. The lighter Ford Blue is said to be very good. Their Red Wagon has been 50/50 for me.
The Red Mirror works fantastic, but is just polyester so not as durable. But it attaches great, and wets out like crazy.
(edit) if you are still having massive problems, you can send me the molds and I'll give it a try. From my experience, the larger the round, the easier it is to cast them. I don't have any sizing dies for 457, so can't finish the job.