Canyon Battle
"Well... Your Highness. The weapon's power is beyond what I could even dare to evaluate. But after using it in actual combat, there were a few inconvenient points."
"You can speak freely."
"Yes! Well... after firing about ten rounds in a row, a lot of black residue builds up inside the barrel, making it very hard to push in the next bullet. So the loading speed noticeably slows down as the fight gets longer."
This is a chronic problem with rifled black powder firearms.
The phenomenon of fouling building up in the rifling grooves cut into the barrel to impart spin on the bullet.
I'd read in books that even on Earth in my past life, this problem caused quite a headache during the transitional period of firearms development.
Of course, the gunpowder I used for the magic muskets was a mix of black powder and a small amount of magic stone dust, which compensated for some of the drawbacks.
But mixing in magic stone dust only helped with easy ignition and vulnerability to moisture.
It couldn't prevent the massive amount of combustion residue.
"And there's one more thing. My shoulder hurts too much when marching. Maybe because of the padding in the stock, but it weighs quite a bit, like carrying a lump of iron..."
"Mm-hmm, that's true. You felt like throwing it away while marching, didn't you?"
When I nodded in agreement, Eric's eyes went wide.
He probably thought a royal like me wouldn't know the pain of marching.
'I wanted to attach wheels to the stock and drag it along.'
"There's a way to solve the loading problem."
"Really, Your Highness?"
The complete solution to the fouling in the rifled barrel is to develop smokeless powder.
But developing smokeless powder would take quite some time, so for now, changing the bullet shape is better.
'Even if I can't use this method for the next battle.'
Because the front here will continue.
It would be right to change the method from the next production run.
'For now, using Minié balls is the best.'
If you hollow out the bottom of the bullet slightly, it becomes very slightly smaller than the barrel's caliber.
So even if there's fouling, it slides in smoothly when loading.
You might ask, won't the bullet not engage the rifling and spin uselessly, reducing power?
That's correct.
But when the gunpowder explodes, the massive gas pressure hits the hollowed bottom of the bullet hard.
The bottom of the bullet expands widely, engaging the rifling perfectly, and it flies with spin.
It was an invention by a French army officer that changed the history of black powder firearms on Earth in my past life.
Finishing my thoughts, I looked at Eric and opened my mouth.
"From the next supply, I'll change the bullet shape a bit so it flies smoothly even with fouling."
"Ooh...! As expected of Your Highness!"
"And the shoulder pain is because you're carrying it with just one shoulder or hand."
I'll need to make a sling for this.
"I'll make leather straps that distribute the weight across both shoulders, chest, and back. I'll send the design to the workshop right away, so bear with it a little."
"Thank you!"
Even with a sling, the gun being uncomfortable can't be helped.
'Because even in modern times, that wasn't solved.'
It's not like you can carry just the gun on a personal drone.
Thinking that, I looked at Mila, who was staring at me intently from beside Eric.
"How about you, Mila? Was aiming or recoil control difficult because of your small build?"
Mila clenched both fists and answered with sparkling eyes.
"No problem at all! Thanks to the device Your Highness designed, the recoil is manageable! Aiming is doable too! I could put a hole in those Empire bastards' heads right now!"
"R-right."
Her excited face looking at me was burdensome, so I turned my head and continued.
"Good. I'm glad the weapon suits you well. Both of you have good training results, so I look forward to it. Full-scale battle will start in a few days, so take care of yourselves between training."
"As you command!"
"Yep!"
After encouraging Eric, Mila, and the instructor, I left the training ground.
I collected feedback on the weapons.
I checked the soldiers' morale.
Now I just need to prepare to face the approaching enemy.
'But I'm a bit anxious.'
Three days remain until Margrave Kraus's army arrives.
No matter how much gunpowder we use to blast a path, we might not have enough time to reach the bedrock of the rocky mountain.
If we can't dig the tunnel in time, the plan to collapse the mountain will be compromised.
'I'll need help from the knights.'
I moved my steps toward the temporary training ground where Seria's knights were training.
"My lord! You've come!"
"Yeah. Is training going well?"
When I arrived at the training ground, Seria, drenched in sweat, ran over with her black hair flying and gave a crisp, military salute.
"Yes! Everyone is training hard to fully adapt to the new weapons."
Seria looked ready to sweep away the Imperial army at any moment.
"The spirit is good, but what you need to break right now isn't the Imperial army."
"Huh? Then what...? Whatever it is, just give the order!"
Whatever?
Then I have no choice...
"That mountain."
"…Huh?"
Seria blinked in confusion.
"You see that canyon where the enemy will come over? The engineers and miners are digging a tunnel there to plant gunpowder."
"A tunnel... you say?"
"Yeah. But it seems like it'll be tight to finish digging in two days with just the current manpower. So you guys go help."
Seria's mouth fell open at my words.
"Ahem. If you dig quickly, I'll make you delicious food."
"Delicious food... you mean like that braised ribs dish...?"
"Yeah. I'll make something even tastier."
"Gulp... Something even tastier...!"
Imagining eating delicious food, Seria swallowed and her eyes sparkled.
She seemed to have set aside her pride as a knight in front of delicious food.
"My lord! You must keep that promise!"
"Got it."
Having driven the point home with a serious expression, she turned around and shouted loudly to the knights waiting in the training ground.
"All troops, attention! Training ends here!"
At her command, the knights all adjusted their weapons and looked at her.
"Our lord has given us an important mission! From now on, we will break through that rocky mountain!"
At the sudden mining order, the knights' faces showed bewilderment.
Seria looked at them, chuckled, and continued.
"If we complete the mission within the deadline, our lord himself will provide a special dish! And he promised it will be even tastier than braised ribs!"
"Ooh...!!"
The knights cheered.
In fact, breaking through the rocky mountain wasn't that difficult for knights.
And since they were promised a dish even tastier than the braised ribs they first ate when they were incorporated into the royal army, they seemed highly motivated.
"Let's go! Break the rocks and eat delicious food!"
"Oooh!"
With Seria at the lead, the knights ran out of the training ground.
The sight of knights charging toward the mountain carrying shovels and pickaxes felt quite surreal.
'Now only the real battle remains.'
Three days later.
As ordered, Seria's knights, the engineers, and the miners succeeded in digging the tunnel in two days.
And they stuffed all the remaining gunpowder from making bullets, which had been stockpiled in the territory, into that empty space.
Currently, I and the knights were observing the enemy's procession from a safe place far enough from the canyon that the explosion's aftermath wouldn't reach.
"Master. The vanguard of the Imperial army will soon enter the canyon."
"Oh?"
At Elisa's words, I focused mana into my eyes and looked around the canyon.
'Oh. They'll arrive in about 10 minutes.'
By focusing mana into my eyes, I could clearly see the countless soldiers and knights approaching in the distance.
'About 4,000 regular soldiers and 300 knights, I'd say.'
Checking the formation, they had the poorly armed regular infantry in the front, with the knights following in the rear.
'They're using the infantry as meat shields.'
In the narrow canyon, they pushed the regular infantry first instead of the high-cost knights, in case of ambushes or traps.
Around the time the Imperial vanguard reached the center of the canyon.
Seria, who was beside me, opened her mouth.
"My lord. The enemy vanguard has reached the detonation point. Shall we blow it now?"
"No. Wait."
"Huh? But..."
"The ones in the vanguard are ordinary conscripts without mana. We can easily beat them with muskets. We'll blow it when the knights reach the detonation point."
Seria understood my intention and nodded in agreement.
Since we can handle the regular soldiers with just muskets.
There was no need to waste the hard-made trap.
'It's too cold-hearted, but.'
This is war, so it can't be helped.
We waited quietly, minimizing our presence as much as possible.
Once the thousands of infantry in the lead passed safely.
'They must be convinced there's no trap.'
The knights following behind let down their guard and began to move, gradually increasing speed.
The knights, their silver armor flashing, finally stepped into the deepest and narrowest section of the canyon.
"Master. The enemy knights have entered the target point."
Elisa, who was beside me, reported in a calm voice.
"Good. It was worth the wait."
Those guys are probably already drunk on the thought of crushing us.
But I have no intention of fighting them head-on.
'This is what war is.'
Without hesitation, I pulled hard on the lever labeled 'Ignition Device Mana Injection'.