I took my longest at 808 metres, with my 7STW running 168g ABLR. Usually, I would be hunting that particular area (New Zealand) with either my 264WM or 300WM, but I was talked into using the barrel screwed on at the time. Took a really nice Red Stag, then another the following day at 678 metres.
I have been very impressed with the 7STW, because normally I'm not a 7mm guy, but I now know why people love them, but the other 2, and many others, do just as much of a great job.
Still waiting to stretch the legs on my 257 Weatherby…
Cheers.