Reduced velocity has a dramatic effect on the practical accuracy of a bullet. Shooter ability aside, slow a bullet down dramatically and several things happen. As mentioned, it becomes much more susceptible to wind deflection, a real factor at 200 yards. Next, barrel time increases, meaning that the way the firearm recoils will have a greater effect on where the bullet goes when it exits the barrel. Handling the gun thus becomes much more important, insuring that the way it recoils is the same shot to shot (the shorter barrel of a handgun reduces this effect a little). Some bullets will not shoot well if slowed down too much, particularly if bullet stability caused by the rotational speed is reduced too much. This means that all else equal, shorter bullets may shoot better than long ones unless the barrel twist rate is high enough.
This is just the effect on the bullet. As important - especially for 200 yard shooting - is the velocity spread shot to shot. This is often more difficult to control with larger cases like the .308. One would think that bore size would have an effect, but IME I haven't seen that happen.
I have had outstanding accuracy with low velocity loads in three handguns in particular. One is a 12" twist .250 Savage XP-100, where I got 1/2 moa grouping with 87-grain bullets and AA-5 powder and velocities around 1300 fps. Accuracy was good enough to win a number of Precision Shooting postal matches. Second is a 10" twist BF pistol in .25-20, firing 87-grain bullets at 1500 fps with H110; accuracy was again in the 1/2 moa range. The last is a 10" twist .300 Savage Contender, with 165-grain bullets cutting 3/5 moa groups at ~1100 fps with BlueDot. These groups are all at 100 yards; I did some shooting at 200 meters, and the wind was the biggest factor in groups size - just like it is with .22 RF shooting at this range. The 165-grain MK was less susceptible to wind that the 87-brain .257" bullet, as one would expect.
Not all jacketed bullets need 2000 fps to expand...look at the Speer Varminter for your .308 for example, it will expand well under that velocity.
10% below "starting loads" should have little effect on the bullet, although powders may not burn consistently enough for good accuracy. For dramatically reduced velocities, don't use slow rifle powders, use faster ones to improve ignition and burning consistency. I like BlueDot for most of my reduced loads in larger cases, others like RedDot. Check the following sites for more info:
http://findarticles.com/p/articles/mi_m0BQY/is_19_46/ai_65017381http://members.shaw.ca/cronhelm/DevelopSubsonic.htmlhttp://www.jouster.com/cgi-bin/reload/reload.pl?noframes;read=31006.