.30 Hart... That's very similar to the .30 Lara, .300 AMU, .308 Baer, and .300 Ackley Magnum.
I have a .300 Ackley, and another guy on here has a .30 Lara.
P.O. Ackley stated (in one of his books/manuals) that the .300 Ackley was so close to the .300 Weatherby, that he recommended using .300 Weatherby load data to start with, and work your load up safely from there.