Ain't enough sugar for a dime.
Like Scorch said, 100fps. If you look at Nosler 5&6, they have the 280 in 26" and the AI in 24". Velocities about the same. You'd spend about the same for a longer barrel as you would a custom chambering job. I had a 280 26" barrel put on a Mark X and the chrono velocities were within 3 fps of the Nosler book with 2 different powders.