Depends on what you mean by hard cast bullets. I wouldn't be afraid to use any normal cast bullet appropriate for normal .38 Special loads. Bullets in the 6-7 Brinnell range are almost pure lead and able to be deformed under finger pressure. Bullets in the 10-12 range will work just fine and not hurt anything assuming you are using appropriate loads. It also depends on which 1905's you're talking about. This model was made from 1905 to 1942. I'd be more conservative if loading for one produced in 1905-1920 vs later production ones.

When I think of "Hard Cast" bullets I think of bullets in the 18-22 range. These aren't ideal for any 38 Special loads and are more appropriate for .357 loads.