Re: Range limit on 308 for deer size game.
I have shot a lot of 175's and they are definitely a bit flatter and have less wind drift at long range than the 168's. Some tactical units are switching to them because of this, every little bit helps with the .308 at longer distances.
Not sure about where the end of "lethality" on deer would be for the .308 but two 165 grain Sciroccos completely penetrated through the chest of a big caribou bull at 510 yards for me this past hunting season. I expect that the .308 will be lethal on deer out to what many guys on this forum consider pretty damn far - 700-800 yards - your challenge out there will be the wind. I shot a couple of deer with 175 Matchkings this fall with perfect results, distances were 100 and 320 so not really long range - exits on both.
You may already know this, but the 165/168's have an easily remembered "wind-chart" out to 800 yards. Using a 10mph full value (3 or 9 o'clock) wind the drift in MOA is one number lower than the first digit of the distance. 10mph full value wind at 500 yards drift the bullet 4 MOA etc.. At 800 use 8, 900 = 9, and 1000 about 10. The 175's have about one minute less drop and wind drift at 1000. This data is from Black Hills Ammo and it works.