The problem is "hard cast" is a general term, and doesn't indicate what alloy was used to make the bullet. A bullet that is hard but brittle will come apart as you found. A bullet that is made of a more ductile alloy will not come apart. If the manufacturer used linotype or a silimar alloy then the bullet they produced is hard and brittle.
The only alloy I've used to cast bullets is wheelweights, which yield either a moderate hardness alloy when air cooled, or a hard but not so brittle alloy when heat treated. I've tested my water quenched ww bullets at 1200 fps in glacial silt, and have had them shot at 1100 fps into wet newsprint. Both of those media showed only minor bullet deformation, and deep penetration.
My suggestion is to cast your own bullets out of ww's and add some tin to increase ductility. I'd consider the bullets you bought as a poor bullet, especially at the relatively sedate velocity of ~1000 fps.
Last edited by 458 Lott; 10/11/12.
