Here is a wright up from hammer head's web site. They use riffled barrels but they talk fairly in depth about various testing they have done, controle methods, results, ect. hammerheadpaintball.com - Technical Information
One thing I saw when reading both flasc and hammer head sites is they both attribute different markers to having different results. Above was mentioned how high and low pressure make a difference but also different bolt styles and valve type play a big role in the signature of te pressure wave on the ball.