Will a soft lead round nose bullet expand if it hits bone or flesh?
Yes. I have seen ballistic gellatin tests of percussion cap round balls, and they flatten in the gellatin slab.
"Gunshot Injuries" by LaGarde is particularly interesting in this regard. Col (Dr?) LaGarde was able to examine living Civil War veterans, skeletons, and interview living wounded, Civil War surgeons. He also had an amazing knowledge of pre WW1 wound ballistics. In Chapter XIII the analysis is that the weapons of the Civil War, firing those huge, dead soft lead bullets, created worse wounds than the jacketed bullets of the era, particularly if they hit bone.
Given that the service rounds of the era were 303 Brit, 8 mm Mauser, the 30-6, one should not dismiss the wounding power of a huge chunk of dead soft lead.
I guess I will always remember the account in Col LaGarde's book about the wounded civil war veteran who had a pistol ball or buckshot lodged in his hand. It had been in his hand for decades and he could make it rattle against the bones of his hand. The veteran took great pleasure in the reaction of visitors when he shook his hand at them.