There is no rocket science to the .30-30AI in the 20" levergun. The Speer 150- and 170-grain bullets have a good BC for deer and pigs. They hold together very well.
With the 20" barrel levergun 3,000 fps with the 100- and 110-grain bullets, 2,700 fps with the 125- and 130-grain bullets, 2,500 fps with the 150-grain bullets and 2,350 fps with the 170-grain bullets is easy with any of the medium burn powders. You do not need the super powders. to exceed these velocities with good case life. Good case life - in my experience - begins with using new cases to fireform your Improved cases using 3/4 to full throttle standard .30-30 load data.
You could start and stop your powder selection using Hodgdon 4895 or H335 depending on whether you wanted extruded or ball powder. I found the two powders to be interchangeable grain for grain with the 170-grain bullets in the 20" leverguns.
The only loading step which requires attention to detail is bullet seating. It is pretty easy to bulge the case just below the point of the shoulder even with a good chamfer on the case mouth.
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In todays world the .308 Marlin Express is a good option if you are looking at the .30--30AI. The published Marlin Express load data is just a bit under what you achieve with high pressure .30-30AI loads. The Marlin Express brass is just a bit easier to work with and you have factory ammunition if you desire.
You can make .307 Winchester or ..308 Marlin Express brass easily from .444 Marlin cases if you need to.
If you want the .35 caliber based on the .30-30 or .38-55 cases don't overlook the .350 Maine Guide which is a pretty old wildcat type cartridge.
