Agreed, the hornet has almost no shoulder, but if you are just neck sizing, you should be able to get better groups than that. Things to try:
* Use small pistol primers instead of small rifle primers. The case volume of the Hornet and the small volume of powder do not need as much OOMPH as a small rifle primer provides. This usually takes care of any erratic velocity issues, too.
* While I have read about people loading the Hornet with LilGun powder, and many recommend IMR4227 for accuracy, my best results were with a 40 gr bullet and 11.0 gr of W296.
* Seat the bullets out just a little further than you are currently, reducing jump to the lands.
* Check your rifle's throat: by using a Sharpie, blacken a bullet, then use it to load a dummy round to make sure you are not seating against the lands. If you touch the lands, it will show up as light scratches on the bullet all the way around. Best accuracy will be when seating slightly off the lands.