I am no expert on a lead hammer but, if it needs to be hard add pewter to wheel weights when you melt them down. It adds antimony.....(i think thats what its called) which makes it stronger and harder. If you go up to your local tire shop with a bucket they will normally fill it up for $10 or there abouts with used wheel weights... donut rule still applies if you want an ongoing relationship with them lol.
Sorry for the long post I got excited to talk about something on here that I have a working knowledge of lmbo.