I've had several Hornets in the past and my current one is a K-hornet that shoots like a house on fire. In the standard Hornet I've had excellent results with 11 gr of IMR4227 and a Winchester 45 gr HP manufactured specifically for the Hornet's velocity range (I buy these in bulk 1-5000 at a time). You can use bullets for the .222/.223/.22-250, but the jackets are generally too thick and they usually won't open well, if at all. I've also had good results with AA #9, 2400, H110 and L'il Gun powders. Use a pistol primer instead of a rifle primer - the Hornet is a small case and doesn't need all that flame to get things going. The rifle primer will do weird things to your accuracy also.
The other thing that seems to help is to neck-size your brass when reloading after they've been fired in your rifle. This step seems to centre the cartridge in the chamber better and contributes to accuracy. The only way to be truly happy with a Hornet is to handload for it - save a ton of money too shich just translates into more shooting.
Hope you have a blast with it...
Blake