At some point, the auto-turrets came on; twin-linked heavy bolters, laying down a high volume of fire in support of the security troops; there were columns, lifts and open-landing floors, and turrets hanging from the ceiling, on tracks, positioning themselves and cutting loose as it detected Astartes.

The Argyosians were putting up a stiffer fight now, too. Autoguns in the hands of some, but more and more had lasguns and were laying down an extreme sort of fire. Prodigal Son took stock of what he had to counter the weaponry. There were grenades in the launcher, but nothing of use to foil the sensors of the turrets. There was the boltgun, but the shot would have to be perfect or the heavy bolter fire would probably shred him. He returned fire with his boltgun, conserving ammo, using single shots to make every one count. Now was the time for cool calculation, rather than being cut down. Now was the time to figure out a way to make it work, however one could.

There was, also, of course, the cannon and its ammunition.

For the first time, deeming it alright to do so in dire circumstances, Prodigal Son spoke. His vocal cords were rusty from a long period of enforced silence. But, he deemed, it was better to speak up in battle than die silently and the duty to the Emperor, the penance, be undone. 

"Iron Warrior. The ammunition. Do you have anything to set it off with?"

Straight for the throat. He kept up a steady pattern of accurate fire, of lives measured and cut precisely according to the fine hand of a Space Marine. But the ammunition was finite, and there were more traitor lives than bolter rounds. They needed to kill as many troops as possible with the minimal amount of resources wasted. By the same token, he aimed for the enemy officers; when he saw one that looked like they were giving orders rather than merely carrying them out, he loosed a bolter round at them. It was a way to sow confusion and a favored tactic of his Legion. They liked to kill the leaders and herd the sheep.

But this little play could not go on forever. They had a mission. The governor had to die.