Alright first thing is whats your barrel length and is this factory or hand loads did you chronograph the loads? The reason I ask is barrel length makes a difference in velocity if your reading it off a box of factory ammo, the test barrels typically run 20"-24". If your running a 16" barrel there is no way your getting 2650 fps from factory loads but you might from a warm hand load ( ask me how I know ::) ) If they used a 20" test barrel and got an average of 2650 your probably only getting 2550 from an 16" barrel, its common to knock off 25 fps per inch shorter your barrel is compared to the test barrel.
I just finished using an chronograph for my 168 gr A-max hand loads and they run 2575 out of my 16" barrel DPMS rifle I then went to Hornady web site and used there ballistics calculator and came up with this. Hope it helps.
Ballistics Calculator - Hornady Manufacturing, Inc.pdf