Well people either love or hate Chuck Hawks but read this:
http://www.chuckhawks.com/rifle_barrel.htm

Towards the end he takes agreeing estimations from both the Remington and Lyman's publications. The way I see things you can hope for 25fps per inch from this data. The 2500-300fps class is agreed upon as a 20fps loss or gain per inch. You are a little past the 2750 average so that goes in your favor. This is with 22-26 inch barrel being considered. But there's a point of diminishing returns somewhere in there so an honest guess would put you back at 20fps per inch.

This is all just theory though. Different cartridges behave differently, different powders behave differently, and some barrels are just faster or slower than others. Even if you reload you will only have control over one of these variables.

Is an extra 4" of snag and muzzle heavy weight worth an extra 3.5% velocity?