Keep in mind that higher elevations like we have here in the Rocky Mountain West will give us much longer supersonic reach. .308 has enough trouble at 600yds if the winds are strong enough and shifting.
With 168gr SMK anywhere near sea level, you're not going to have a good day trying to hit IPSC silhouettes at 1000yds. I've had enough trouble doing it with 155gr Scenar hot loads from a 24" bolt gun (.308 Surgeon) in Colorado in shifting winds. I was chasing the wind with every shot, and vertical dispersion became an issue as well.
I gave up on .308 years ago because of the 6.5mm's. It's a waste of my time at anything past 700-800yds, even at my altitudes where I commonly shoot, and because I often travel to shoot competitions down at sea level. I wish .308 was never born, to be honest. If I could go back in time and abort it before birth (within Army Ordnance Board .30 cal nazis), I would stomp its infant carcass into the trash. There were much more efficient cartridges being developed at the time that should have been selected, but because of egos and incompetence, were not.
The only redeeming qualities of the 7.62 NATO and .308 are that you have excellent barrel life with them, and they are well-vetted for accuracy, components, and market support.
For an 11.25" twist, the longer shank pills like the 175gr SMK aren't going to do as well as they would with a tighter twist. I think Todd Hodnett is onto something with the short bull barrels and tight twists for extreme long range, since stability factor is better as the bullets pass through the transonic region.
Another affordable bullet to look at for .308 with 11.25" twist is the new 155gr SMK Palma. At the end of the day, you need a very experienced and dialed-in spotter who is providing wind calls every second in ~10mph or more winds for the .308 Winchester and an exceptionally accurate rifle to have high hit probability on targets just within 700yds, even at higher altitude.
