Most test I have read have to do with jhp ammo jell penetration. I recently read another test concerning bone penetration. Since the chest area is protected by bone. The test indicate that jhp ammo may not penetrate through the bone into vital area. Whereas fmj Ammo would. Tests seem to be in conflict 9mm round nose may in fact ricochet off the bone and not penetrate. 40 cal flat nose would crash through the protective bone and penetrate the vital area.