No way is 2" 300fps. You MIGHT get 50fps per inch but usually its less than that, often no more than 25 or 30.
QuickLoad tells me that a 28" barrel on a .308Win will launch a 150gr Nosler Accubond at 3,052fps and a 20" barrel will do 2,816fps.
Total difference 236fps, average of 29.5fps/inch.
The difference between a 20" and 16" is 97fps, 24.25fps/inch.
So from 28" to 16", you lose about 335fps, an average of 27.91fps/inch.
Last edited by Brian Pfleuger; April 14, 2013 at 07:54 PM.