Roughly 1997 creating grooves by using electricity to erode metal superseded broach cutting in S&W production revolver barrels larger than .22 caliber. Lands and grooves now have rounded corners and some barrels appear nearly polygonal.
While some cast bullet shooters are getting good accuracy without significant leading others are having a devil of a time. EDM rifling and cast bullets is controversial but the majority of casters on the big forum for S&Ws are happy with EDM barrels. It could be the casters who are having trouble need to tailor their loads to their new revolvers rather than stick to their tried and true loads for broach cut barrels.
I mostly shoot older revolvers. My only experience with cast through one of the new barrels has been great accuracy and no leading firing bullseye power level .45 ACP. Lacking experience firing magnums my only opinion is that the jury is still out and EDM rifling is a consideration for home casters looking at newer S&Ws.