Clock

"Ten-nine-eight..." Her little brother was counting aloud, his not-so-secret girlfriend watching, trying not to say anything. Sophia and Cynthia had been through a lot together, though, so she wasn't throwing the book at them, even if it had made their other brother unhappy, well so she presumed, Niels hadn't said anything. They were here to observe a test, of which Dacapo had done a lot of prep work for, mostly using enough math about airspeed, moisture and wind direction to make her head spin.
On the zero, the shell disappeared into the ground, and Dacapo started counting forward again: "One, two, three... on ten, the ear protectors anticipated a pressure front and activated, and Sophia and Cynthia could hear nothing. They still felt the groundquake a few seconds later, the kilometer seperating them from the target crossed in minimal time. The shell had dug a sinkhole perhaps two hundred meters across, and nothing of the target remained. "Test successful?" Dacapo asked his big sister, his excitement making him almost vibrate.
She didn't answer immediately, tracking her officer's binoculars across the field, the hillock they had just targeted was for all intents and purposes gone, turned into a deep hole in the ground, some of the sand looking... wet? That'd probably be quicksand then... She made a note to mark it as such on the regiment's maps. "Test successful, wildly successful, good job lil bro."
Cynthia's binoculars turned ninety degrees from the sinkhole and she barked: "We have bandits inbound, nine seven two." She opened a circuit to the nearest airbase. "Base traffic control?"
"This is Uridi Minor Airfield."
"Uridi Minor, This is Senior Captain Cynthia Goldenrod, support company, first battalion, 8745th Montral Fusilliers I want to signal chaos vehicles, Brass-scorpion-class, four strong, nine seven two from forward observation point gamma, please acknowledge."
"Acknowledged, Captain Goldenrod, we've been tracking them for the last minute, floating observation platform Uridi-two beat you to it, but they have a klom of elevation to help their eyesight, good job finding them from the ground, wish all of the Emperor's soldiers were quite so vigilant. Uridi-minor out."
"Uridi Minor, I want to reach my command, but I don't have the range on this comm, please relay that information to seventh and eight battery, support company, first battalion, with my compliments and tell them I want clockwork shells on target as soon as possible.."
"Uridi Minor will comply, Captain Goldenrod, out."
"Clockwork shells?"
"Dacapo's idea, since they're timed to burrow into the ground"
A downcount from 20, and a count of ten later, four shells had dug into the ground underneath the abominable chaos siege engines, blown up, and while one had survived, it had lost its tail and at least two legs, perhaps four, and was trying to wrestle itself out of the hole.
"Consider that a field test validation, boss-budget."
"You know I hate that name!" But Sophia was smiling, diminutive name derived from her fuss-budget one or not, killing the best part of one of the monsters per shell was exceedingly tidy business. "Cynthia, my compliments, seventh and eight?"
"Yeah, first was busy here with the test."
"Aw come on, leave some work to do for the other crews, I know first works really well with my little brother, here, but you have trained the rest of them well too."
"That's why first was here for the test, Dacapo went in and measured the wear in each of the tubes for this..."
"Was that totally necessary?"
"No." Dacapo hung his head.
"But we didn't know that yet, we didn't know if the equipment unbalanced the shell or if the pendulum inside would swing the shell in any weird directions yet, not until this test..."
"True." Dacapo was rubbing his chin.
"And they didn't?"
"No, if anything, the clockwork shell is exceptionally well balanced, the shot had a tolerance of fifty calibres out at that range, and we hit on-target to five or so calibres."
"Well, this test is done, back to barracks for everyone."
Cynthia called first battery. "First battery? Roll for home."
Crackle, crackle. "Earthshaker unlimbered, Captain, ETB 2 hours."