Swaged bullets are made by mashing pure or almost pure lead into what ever shape is needed. Naturally they will be very soft around 5-8 BHN at least as far as I can tell with my goofy Lee hardness tester. Cast bullets will almost always be a lead alloy made up of lead, tin and other metals. The tin and other metals improve the casting properties of lead and make it harder. While it is natural to assume hard lead will work better keep in mind the key to no leading is that the bullet be bigger than the bore (or chamber throats when it comes to revolvers). An undersized bullet will lead the barrel period, does not matter how hard it is. Bigger diameter is always better. Its important to measure your bore or chamber throats to make sure your cast bullets are at least 0.001-0.003" larger.