jeebus @ mmw
+1y
ive done it in the past on a mill.
sometimes run an end mill, perpendicular into it, sometimes they drill a hole strait through, it depends on what style your looking for.
Ive heard it called alot of things, i allways call it machine gun style, just because alot of older machine guns have barrel shrouds that are done that way, to protect your hands from the hot barrel.
ive never heard of it done with a dimple die, and im not sure that its possible or desireable that way.