Sounds like a good place to start, but I had no luck with .380" hard cast in my 38-55 shorty, couldn't hit the target at 100yds, .381" wouldn't chamber before the neck ream. My 28" Target shoots Cheycast 1:20 gas checked(see FAQs) .380" 325gr Snovers fine tho, I think the softer lead bumps up enough to be accurate, something the hard cast just wouldn't do even at higher velocities. I do have some Hunter Supply .381" gas checked to try in it now that it's been neck reamed.
Tim