Try to get to a 22" barrel, otherwise you will be giving up the velocity (and range) you will need for longer mountain shots.
Personally I am going from my 6.5 CM Browning X-Bolt Pro (22" barrel) to that very same rifle in 6.5 PRC with a 24" barrel. The bare 6.5 PRC rifle weighs 6 lbs. 3 oz. due to having a carbon fiber stock and extensive fluting on barrel and bolt.
That 24" barrel length is about my max length for hunting. I'll lose a bit of velocity from the "ballistically ideal" 26" barrel but hey, it's a hunting rifle.
Eric B.
BTW, jebel is right, the Barrett Fieldcraft is a great rifle for the money. Truly high quality.