It has to extend to all 168s to some degree. Even the finest and pointiest .308 VLD design still has to measure .308" around the middle - so unless it's heavier, it can only be so long before you run out of bullet... No matter how you cut it -- 168s are shorter and fatter (proportionately) than heavier bullets. I concede that (at long range - and only comparing MATCH bullets) a GREAT 168 might be comparable to a mediocre 175.
By the numbers - I launch 155s over 3000fps, and they handle the V-ring without problems back to 1000m. They're shorter than 168s - but so damn fast that they're still going through the paper supersonic.
I used to launch Hornady 178 Amax at just over 2800fps. They're fine, too. They're a higher BC bullet and they keep more of what they have -- and probably cross the finish line at the same speed (just a bit later) than the 155s. I used a lot of 175 Sierras as well. Similar loads to the Hornady bullet. Can't remember the velocity -probably similar. HAd a supply problem with them a few years back so migrated over to Hornady for a bit. Kind of remember bweing a bit happier with Sierra... what can you do?
I shoot issued 168s that don't make it to the finish line. (Norma. Good stuff. Uses the SMK in their cartridges) I forget what they chronied at. I keep them around because it's good to know what they do in case I come across (if it's given to me, for example) some Winchester Ranger stuff at a match, I will use it for movers or other applications since it's cheap and perfectly good for the ranges it was designed for (300...) and back as far as 600 or even 800 in a pinch.
I got a steal of a deal on a huge pile of Hornady 168s that I've loaded up and I get great performance at medium ranges, and velocity in the ballpark of 2900fps -- so it might be OK a bit longer than the Norma stuff the Army used, or the Cop Ranger stuff. But I'm not going to bother worrying about it. I keep it for barrel dirtying before matches and practicing reduced course matches at 100m... rough zero confirmation after lifting a scope of a base...
heavy versus light:
There "might" be some merit to the heaviest bullets out at long range. Maybe they start slower - but if they cross the finish line at the SAME SPEED as the lighter bullet - they have MORE ENERGY to hand over to the target. No matter to me, since targetry is fairly lightly armoured and doesn't take much to kill.
And even if you're "working" or hunting and terminal ballistics matter more to you -- remeber that "enough" energy drilling into a target is infinitismally superior to five times that amount of energy drilling into the tree beside the target. Only hits count.
I'm sure there are charts somewhere about THAT aspect of ballistics. But the numbers that speak to accuracy of the 308 that I care about are years of data and scores that I have accumulated myself, as well as data from trusted peers. And we have fun arguing back and forth about LIGHT155s versus HEAVY175s. And we bicker about VLD versus SMK and the thickness of Berger jackets, etc. etc. etc. But we don't talk about the 168 bullet in the middle.
Shoots epic good at 300, though.