I"ve heard it called both EDM, and CDM. I don't know which it is for sure. Brian Pearce of Handloader calls it EDM, but my buddy talked to a gunsmith friend of his who worked for Smith, and he calls it CDM.

It will work fine with lead. Although it doesn't usually shoot as well as cut rifling for that purpose, it will generally shoot lead better than most of us can hold on target.

My 586-4 that was built in '95, has that type of rifling, and from what I can find out, that is just about when Smith went to that type of system. It is faster for them to produce, with better consistancy, those being the two main reasons for the switch.

I hope that helps.