From Wikimon

Musou Knightmon is the "Darkness-rumbling Mode" born from the DigiXros of Dark Knightmon and Tsuwamon, in which the Gouradarai Gun was added to Dark Knightmon, so that Dark Knightmon, who boasts of overwhelming power, became an even more destructive and fiendish Digimon.

The one and only "Chouryoku Meidouha", which emits the two Digimon's energy simultaneously from the Gouradarai Gun, leaves nothing but rubble in the tracks of its bombardment. By casting its "Majūryoku Jubakujin" on its surroundings before firing, and restricting the opponent's movements, it can both keep from missing its target, and also be defended while firing. The shock wave when it fires is earth-shattering, and is enough that things sustain damage only by being in the surrounding area, even if they are not hit directly. After a bombardment at its maximum output, Musou Knightmon's power is set aside for forced cooling of the gun barrels, and it cannot fire rapidly. However, because it seems that there is no Digimon that can suffer this technique and remain safe, it can be said that there is no need for firing rapidly.