When I was living in Anchorage (1979-1982) a group of us decided to see what we could do with 30 caliber cast loads. We had a mix of Remington 788s, Savage 340s and H&R Toppers, all in 30-30 Winchester. The 30-30s all proved very accurate and provided all the velocity we needed. But, if I was setting up another .30 cast rifle, I'd start with a 30-30, and have it rechambered to 30-40 Krag. The rechambering would remove any long throat issues the Handi might have, the case is rimmed, tapered for easy extraction, easy to get, has the long neck (which is ideal for cast loading) and should provide all the volume to drive the cast bullets as fast as you would want. The only down side is the micro-groove rifling, but some have stated that is not much of a factor. If one could find one of the older H&R (pre-micro) rifle/barrel, so much the better. Just my thoughts.
Wally