I've run a sample pack of 250 Blue Bullets and over 1000 SNS Casting coated bullets through my Hornady Bullet Feeder die. I watched this Youtube video to help work out some of the issues.
https://www.youtube.com/watch?v=bJro27cx0yA
Coated bullets dropped fine through the first collet, but would get hung up on the bottom collet. I used 400-800 grit sandpaper wrapped around a pen/dowel to smooth out the inside of the bottom collet. Additionally, you can use something to expand the prongs on the collet to help the bullets drop through. The end of a Sharpie marker worked for me. I then used a Dremel with a felt polishing tip to smooth out both collets. I repeated the process a few times until I got bullets to feed consistently.
Using mixed brass, I took the case with the shortest length and flared it to .385". Longer cases run through the expander die will get more belling, but .385" is about the minimum bell needed to get reliable bullet feeding.
When setting up the die, I think I had to back out the adjustment screw more than the 1/2 turn listed in the manual. It took a bit of fine-tuning, but the die works great now with home-made bullet feeder tubes made from plastic tubing. Here's the link for the home-made bullet feeder tubes.
Home-made Bullet Feeder Tubes
I load 5 bullets in the die and 45 in the tube, so when I pull out the hitch pin on the tube, the stack of bullets doesn't fall as far. I've never had too many bullets feed, but early on a bullet would occasionally fail to feed. I loaded 400 rounds just last night without any issues with the bullet feeder die and home-made tubes. I don't recall having any bullets fail to feed from the die in my last few reloading sessions with ~200 rounds loaded per session.