Indexing causes powder to spill from cases

First, push down on the edge of the shellplate at the bullet seating station. If it feels springy, then tighten the shellplate bolt down a bit more. Be sure you bring the handle up at approximately the same speed to pull it down at.  Don't "slap" the handle up. If all else fails, you can cut off up to 1/2 coil from the detent ball spring.

I have the same problem (with pistol cartridges) and find that in most cases, the amount of powder appears far greater than it really is...check it yourself.  I assume you are lubing the cases. I use the Dillon spray lube and it obviously lubes inside some of the cases.

I have found that a smoothe operation of the handle both down and up (I always finish a stroke with the forward primer seating motion) keep powder spillage to a minimum but won't stop it. My biggest "hangup" comes from the pistol cartridge snatching on the expander tube at station 2 on the upstroke (this is where the occasional very light inside lubing helps). If you feel it grabbing, just slow your stroke.

Try loading about 50 rounds at half speed and go for "smooth" operation. Then speed up but keep smooth operation. Also make sure you have the shell plate well fastened down and backed off just enough to get a smooth rotation...but no loose (don't want much if any up/down play).