[Xringshooter]

With the additional info provided it could be hot reloads that were put into the PMC box. That said, splits as you describe can come from weak cases (reloaded many times), very hot loads, loads that have chemically changed over time (this is rare), or oversized chambers. The person who fired them did say they didn't feel right. The Super Black Hawk is an extremely sturdy gun and can typically handle some pretty hot loads.

Take the gun to a gunsmith (a gunsmith, not necessarily a gun dealer) and have them check the cylinder diameters to insure they a not oversized for some reason. If all is correct then get rid of the remaining rounds and have fun shooting it. You might want to get some 44 Special rounds or have someone load you light 44 mag rounds. The SBH is a fun gun to shoot.