Any idea how far your staying supersonic?
For a quick and dirty answer use Berger's ballistics calculator on its website which has the 168 VLD ready loaded in its database.
At 59-deg F and 0 ft ASL, it says this bullet at 2,740 fps goes subsonic a bit short of 1,400 yards and transsonic flight starts maybe 200 yards shy of there. However, work done by the US Army many years back on the old 173gn FA FMJBT match bullet showed that transsonic negative effects didn't really kick in until the bullet was down to 100 fps above the speed of sound, ie ~ a retained speed of 1,225 fps which occurs a bit before 1,400 yards in this case.
BUT, change the environmental parameters to those quoted by
@sandwarrior ie 95 deg and 4,000 ft ASL, and you obtain a big plus through the thinner air reducing drag. Subsonic transition moves to a bit the far side of 1,700 yards and the 1,225 fps speed-point isn't reached until nearly at 1,600 yards.
When going out to these sorts of distances and nudging the speed of sound basic calculators like this using average G7 BCs start to show limitations so these figures are a guide rather than written in stone. But they're pretty impressive from such a small cartridge.
With
@sandwarrior mentioning the 123gn 6.5mm Scenar in the older Chuck & Scotty video range tests, I used to shoot this bullet at up to 1,000 yards in F-Class at not very high MVs. This is a stunning long-range performer and can produce amazing performance and precision in the little 6.5X47mm Lapua. I sometimes wonder how well it'd do in today's hot 6.5mm Creedmoor loads (as used by Chuck in the older video) in F-Class but everybody I know using this cartridge seems to choose the 147gn ELD and/or are experimenting with the new 150s these days.