I was told that Lapua's 300-grain Scenar load put all others to shame and was not let down. Twist rates are moving in tighter directions, enabling longer (heavier) projectiles to be adequately stabilized out to long ranges.
Years ago, I learned large projectiles need some distance to settle down and shoot pretty groups. At the other end of the spectrum, high-velocity projectiles begin to exhibit unstable flight characteristics as they move through transonic velocity into the subsonic realm. Popular designs like the Scenar and Sierra's MatchKing use a boattail to help smooth this transitional flight period.
I tested the Barrett MRAD with Lapua's 300-grain Scenar at 70 degrees Fahrenheit, verifying muzzle velocity at 2,790 fps. In that environment the bullet was subsonic for more than 1,500 meters. Vertical dispersion is another critical component to long-range accuracy. The 300-grain Scenar load's vertical dispersion averaged 4.75 inches at 800 yards, which is very manageable. The bottom line is, "I wish I had it back in the day."