With the proliferation of accurate bolt rifles in 6.5 Grendel and light weight bullet for varmints would be great. Something like a Varamageddon at about 75gr for colony varmints would be great.
The sierra 85gr HP has always been a favorite for song dogs and other varmints in the 260 and would be great in the Grendel. I've yet to try it in mine. If you can find the Federal AE Varmint & Predator 50 count loaded with the 90gr Speer TNT it is very good. Near 2900fps out of my 18" barrel and under MOA.