If you don't have access to a large supply of hard lead, already. You will enjoy many hours of searching for a source. Lead is getting to expensive and hard to aquire cheaply. Soft lead cost to much to alloy harder if you have to buy from Roto metals, .. In a couple of years it will be cheaper to buy already cast , some times you can buy bulk cheaper now. try Castboolits.com for lead. going price is about a 1.00 a pound shipped. ..
Ebay is a guess as to what you are getting. And you will be learning about Zinc pretty fast.
Mike