When I kept losing one of the drones the local violin shop owner
recommended I switch to a wound synthetic gut string and showed me how
the breakage point on the drone was right on the ear, which made a
sharp break. Since the switch I've not had the drone break. It sounds
like I'm now using something very much like what you use.
For the chanters I have similarly had no problem with breakage on
metal strings because the nut is not a sharp bend, but is instead a
gentle curve. It really all depends on the geometry of the instrument,
but for instruments with the traditional style ear on the drones,
metal core drone strings can be a liability.
-Arle
I use Dominant strings as drones which have a core from synthetic
fibers and are metal wound. By the way, the metal rope core strings
I use as chanters are extremely flexible, much more than plain gut.
I never managed to break their core, its always the flat wire spun
arround it that breaks.
Simon