When used, the Gunner fires a small flame burst, then propels himself/herself with a stream of flames (which deals no damage) from the arm cannon. The Gunner can then control the direction that it travels during the launch, with the range being from straight upwards to nearly horizontal. The move overall is similar to Pit's Power of Flight, but with about half the distance.
Arm Rocket goes around the same distance as Lunar Launch, but has plenty of differences. Lunar Launch has the advantage of doing damage, being a quicker move, having less landing lag and retaining its momentum after it's over. Arm Rocket, however, can be aimed in many directions, allowing for more recovery options and making it harder to predict than Lunar Launch's always-upwards movement.
Special Move customization was added in Super Smash Bros. 4. These are the variations: