Re: 20" 700 tactical load help (308)?
Whatever you use in your gun, bullet and powder wise should be fine. Granted the rifle could be picky and not like the bullets you use but they will both shoot the same stuff. Only difference being the velocity loss of a 20" barrel versus a 26" barrel. You can use Scenar's, SMKs, VLDs, A-Maxs, TTSXs etc, the list goes on and on. Powder choice will be the same for both guns as well, however the powder CHARGE might be different due to pressure issues and whats more accurate out of the various rifles.
You will have better luck looking through the "Reloading" section of the forum for more information, a lot of good reading, especially for the .308. That's where I have gotten most my information in addition to the reloading manuals I have at home. By the way there is FGMM in both 168gr and 175gr SMK, Horandy has teh 168gr A-Max as well as their new 178gr Superformance. Black Hills, Corbon, and Lapua also sell match grade ammuntion already loaded. There are others that sell match ammuntion as well.
EDIT: The 168gr SMK has a transonic 'tumble' anywhere from the 700-900 yard line depending on the initial starting velocity. The 168gr SMK was desinged for 600 yard benchrest (correct me if I'm wrong gentleman) shooting and excels at that range, however it fails after that. The bullets becomes unstable and becomes very difficult to shoot beyond this transonic range. People do shoot the 168gr SMK out to 1000 yards but there are much better bullets than the 168gr SMK that can be used.