[Pecos]

There are many alternatives. Lead-free pewter has a melting point on the order of that of lead. Barnes makes all-copper bullets. Ingenuity will always find solutions.

[Falcon4.0]

It's the weight that makes lead so good as a projectile.
It carries more energy. They found out when they banned lead shot for Water Fowl that the steel shot was wounding more Birds. They started to use Bismuth which has a high density, but it was expensive.

[catman67]

Would most likely be declared “armor piercing” by the BATF.

I heard of one brand of cartridge that had a hard lead alloy core that the ATF deemed armor piercing and denied further import.