The diameter is the least of your issues. Anything from .355 to .357 should be ok, if not necessarily ideal. Your gun will have it's own preference.
IMHO, you very likely have a powder measurement problem. Itty bitty powder charges can be a PITA to get consistant in a lot of measures.
FWIW, I reload cast 95 & 100 gr bullets in .380.
"We have normality. I repeat, we have normality. Anything you still can't cope with is therefore your own problem." Douglas Adams