We're doing 2 days of Long Range this year, just because of stuff like this, man. Day 1 will be "serious day" just to run our real long guns. Targets stay up that night, because we're running an 850-yard night shoot. Next day is for stuff like you're talking.
If a 12.5" Grendel can run 850 - other stuff should, too. I'm picking up another LaRue LT-158 with the QD levers, and setting up a permanent scope in it - just so we can slap it on some of the short guns and run them at distance. After running the 13.5" .308AR to 400 yards with a red dot on it - I want to run it longer with magnified optics. The 12.5" needs stretched out, too, just like that. Both those guns are red-dot guns. Let's give 'em some glasses, so they can see further...