The term "hardcast" and ''hunting projectiles'' are not really compatible. Anything much over 15 or 16 Bhn is getting into the area of brittle, likely fragmenting at higher velocities. Below say 15 Bhn and softer, then we are talking a soft ductile bullet that holds together well. Millions of buffalo were killed with Bhn 10 or so.
Fragmenting depends on the antimonial content, nose and impact speed.
Wheelweight metal has the same attributes under 15 BHN as it does up to as hard as they can be heat treated, which can exceed 30 BHN, the "reaction" is also similarly dependent on what is posted above, as it is for any lead alloy.
High antimonial alloys fragment in large, non- ductile pieces; wheelweight and similar alloys are not high in antimony.
Softer bullets don't always hold together well either. It all depends on my first sentence.
The 357 Magnum (or even a 357 Maximum or 35 Whelen) is not going give any problems in the hunting field cast hard with the correct alloy for its intended purpose.
