Wow Rocko,
Didn't know you were a veteran 'Hornet reloader.' If I had known that I would have said try everything that's been a success for you, but then "here are the tips I've consistently heard about ......"
As for the standard primers, they're a lot more "delicate" than magnum primers, and the pistol caps have even softer 'battery cups' than small rifle primers do. Tweaking the primers has been something I read even the best gun writers recommend, but reloading entails much experimenting of course.
I'm surprised Lapua and Norma don't offer brass. Best brass available is usually Winchester - but decide for yourself. As for breaking in a barrel, if you've had success with Handi-barrels shooting right from the box - just remember that isn't always the case. Maybe your Hornet you're trying to get to shoot wants more TLC before it settles down.
Also the suggestions to only neck-size is good, as is crimping the bullet however needed.
I'm going to shoot the K-Hornet to try to eliminate many problems associated with the standard Hornet, alond with providing a better shoulder to headspace with.
You mentioned that you use H110 with much success. I'd recommend also taking a careful long look at Li'Gun. Oddly enough I remember reading that 13.0 grains of that stuff is magic in some Hornets/K-Hornets.
Good luck! Please continue to share your findings and successes.