What Ron said, to a "T".

Revolver cartridges that are loaded lightly can utilize a taper crimp if desired. Anything at normal velocity or above should employ a roll crimp to avoid having bullets "jump crimp" and tie the cylinder up. I think there are other things that can contribute to this, but crimp probably is the main factor.

This would seem to be a fairly rare occurrence; I have been around tens of thousands of revolvers cartridges fired by a lot of folks who were handloaders and never saw this happen.