To my knowledge there is not a standard factory bullet "softer" than the Hornady 220. If you could not get the other bullets you mentioned to expand it's probably due to too low velocity. You didn't state your velocities, do you have a chronograph or access to one? Also you didn't state the distance at which you checked for expansion. Personally, I've never had any problem with expansion with any bullet I've used in the 375 JDJ.