For conventional small arms, differing muzzle velocity due to different effective barrel length killed Metal Storm's accuracy. Eg, the top round in the stack ma

For conventional small arms, differing muzzle velocity due to different effective barrel length killed Metal Storm's accuracy. Eg, the top round in the stack may travel down 6" more of barrel than the bottom round; in a 5.56 gun, this could be a 500fps+ difference (https://rifleshooter.com/2015/12/223-remington-5-56mm-nato-barrel-length-and-velocity-26-inches-to-6-inches/ https://rifleshooter.com/2015/12/223-remington-5-56mm-nato-b...).