Since trying almost subsonic loads in 243, something around 1400 fps IIRC, and 80 nosler varmint BTs, and those performing just like a "normal" deer bullet I think you are onto something with the light varmint ones, they would come close to expanding I'd think at subsonic speeds.
I'd just feel better with a bit more weight behind that, if possible, but high on the list owuld be a way to find a thin jacket 100-120ish grain bullet pushed sub sonic accurately and see what gives.
Thats about the only use I've had for varmint bullets. Though I've been tempted to try 60 vmax in 223 on yotes, but have so many 75 bthps loaded taht work just fine I"ve never bought the 60s yet.
