Re: 7x57 ballistics & brass
According to Hodgdon data, it takes 284 Win or 280AI case capacity to safely reach 2800 fps from a 24" barrel. No way are you going to do that from a 7x57 case at safe pressures. If you go the AI route with a bit longer barrel and just the right powder, maybe. 2700 fps is achievable at modern pressures, though.
I would advise using Norma brass either way. Prvi Partizan might be worth a try, as well. I started out using Remington brass in my Ruger #1A. I am not happy with it.