I shoot against a fella from Northern Illinois that competes with a Savage .25-06 in 1,000 yard matches. He shoots the heavy Bergers as I recall & most certainly does NOT embarrass himself. He usually scores around 190 or so out of 200 from that distance...not too shabby.
Randy Was out last August with a guy shooting a 300WSM(one of Bruce Artis creations)trying to get into the 2000 yard club.Had the 50 along so when he was waiting for his barrel to cool I figured I'd give it a try.To my surprize it stayed very close to MOA out that far but unfortunately a Prairie dogs is smaller than 20".Ran out of ammo before a prairie ran out of luck so to answer your ? no it aint happened...yet. Good luck with your 5000 yard hog.
Contact Precision Shooting. In one of their early 1990s books there was a long article on the 257 Banshee. It was based off the 8 x 68 RWS case which is very good. They were shooting prairie dogs at around 1400 yds with it. Cannot remember any of the details without going back and finding the article but one hot cartridge that worked well.
RWS cases are very good guality, just tough to find in the US. Dave Tooley is distributor and likes the case a lot.