Quoted from thedefog:Tungsten would probably be the closest actually obtainable thing, but even it is only like 2.5x the density of steel.
Other denser of the metals would be Gold, Platinum, Iridium, Osmium, Platinum, Rhenium. Either not possible or too damn expensive. Just looking at periodic table here.
amazon.com link »
That's a spicy meatball
I assume steel is mostly Iron, no? Could go Lead balls?
Why not Uranium?