Those of you that get the American Rifleman magazine have most likely noticed the article on the  SA Socom II. What I zeroed in on was the velocities since I haven't had the time to chrono my Socom 16. There was also a Dope Bag article on the Panther arms AP4 - 308 which also has a 16" barrel. The velocities are as follows:

SA SOCOM II
Federal 150 Gr. Nosler Ballistic Tip           2583 Avg.  Standard Deviation  14
Remington 150 Gr. SP                                 2474 Avg.  Standard Deviation  31
Winchester 150 Gr. Ballistic Silvertip        2517 Avg.  Standard Deviation  32

DPMS/Panther Arms AP4-308
Federal Gold Medal 168 Gr. Match King     2479 Avg.  Standard Deviation  19
Hornady 168 Gr. AMAX Match                    2500 Avg.  Standard Deviation  12
Black Hills 168 Gr. BTHP                             2457 Avg.  Standard Deviation  26

The average extreme spread on groups (@ 100 yards) was  1.01" for the DPMS and 2.75" for the SOCOM II. The DPMS was scoped and since it wasn't specified I assume the SOCOM II was iron sights.
It doesn't appear that the 16" barrels suffer a significant (IMHO) loss of velocity.

Don't most of those 150 gr loads do around 2700 out of 22" barrels? I think 200 fps is significant.

I suppose it depends upon one's ballistical requirements. It averages to a loss of 33.3 fps per inch of barrel (from 22" barrel to 16" barrel). I read somewhere that the loss in velocity per inch would be greater. Maybe I should have stated that the velocity loss is not as bad (or significant) as some of the estimates I have read. I suppose 200 fps could be significant for trajectory and bullet drop, especially at 300 yards or better. At any rate it was the first published chrono data I'd seen and it didn't look to be as bad as some of the estimates I had read somewhere. I should have been more clear.