Thx.

Roughly 25fps per inch, so you should be about 100fps slower with the shorter barrel, all things being equal. Different barrels do different things. For instance, my buddy had a factory Savage .308 with a 26" barrel and I had a Remington .308 with a 20" Mike Rock 5R barrel.
My handload through my rifle gives me about 2685fps, the same load through my buddies rifle gives him 2715fps. The hand lapped, tighter tolerences of the Rock barrel really shines over the factory offering.