Alliant does not list any loads for lead bullets below 200gr, and no jacketed bullets below 230gr. They may feel that it is too fast for lawyer safe loading.
The current Speer manual (#14) shows 4.5 gr starting, 4.9 gr maximum with their 185 gr TMJ SWC. I know that's not the same bullet, but I think it would be OK with your hard cast lead.