# Chapter 58: New Weapons (6)
Having determined the direction for personal weapons, Hyang immediately moved on to work on supporting firepower.
With blank paper before him, Hyang crossed his arms and murmured.
"Considering the craftsmen's skill level, I could be greedy, but other things won't keep up... The things I can actually try have shrunk considerably."
Hyang opened a book he had set aside and examined the lists.
"Singijeon and Hwacha... these also need development, but I need something that will deliver more certain terror to the enemy."
Hyang tapped his fingers on the Singijeon and Hwacha entries while lost in thought.
When it came to Munjong, the most famous items were Singijeon and Hwacha. Their actual combat records were not to be dismissed. However, Hyang felt something was lacking.
"I must show visible results before this year ends. The ministers won't stay quiet because of the budget, after all."
After pondering what would be best for supporting firepower, Hyang finally reached a conclusion.
"As expected, there's only one answer. Bigyeokjincheonroe. Turtle ships at sea, Bigyeokjincheonroe on land. It may be a cliché, but..."
Hyang straightened his posture.
"It's the best for impact!"
Having decided on Bigyeokjincheonroe, Hyang fell into another dilemma.
"I wonder if when actually making it, it would be Mk.1 or Mk.2... Or perhaps Mk.2-1?"
The 'Mk.1,' 'Mk.2,' and 'Mk.2-1' that Hyang assigned were arbitrary distinctions based on 'how it would explode.'
* * *
Mk.1, Mk.2, and Mk.2-1 were things that had troubled Hyang for some time even in the 21st century.
Mk.1 was the scene we typically see in dramas—the gunpowder inside explodes, and the iron fragments created when the iron shell and the pyrites (菱鐵, caltrop iron) inside shatter spread in all directions to kill enemies.
Mk.2, when ignited internally, sprays flames and pyrites through the hole where gunpowder was inserted. Due to the position of the hole, the Jincheonroe spins while spraying flames and pyrites in all directions, inflicting casualties on enemies.
The reason Mk.2 emerged was because the black gunpowder used by Joseon had a slow combustion rate. It was difficult to achieve rapid instantaneous combustion that would exceed the critical threshold in a flash, shattering the projectile body and scattering fragments, pyrites, and flames in all directions. Instead, when the hole that was plugged after gunpowder insertion bursts open, flames and pyrites would spray through that hole. When Hyang first encountered this argument, he tilted his head in confusion.
"Why? Bigyeokjincheonroe has two holes, doesn't it? The hole for inserting the timed fuse, and the hole for inserting gunpowder and pellets. So why only through one?"
Unable to find a clear solution to his question, Hyang simply remembered it as interesting and forgot the fact.
Time passed, and the actual Bigyeokjincheonroe was excavated, with news of an exhibition. Having just quit his government job and preparing a smithy, Hyang recalled his past memories and immediately visited the exhibition hall.
At the exhibition, Hyang circled the glass wall protecting the excavated Bigyeokjincheonroe, examining it closely. After studying the Bigyeokjincheonroe for a long while, Hyang stepped back.
"I solved one problem, but another has appeared?"
The problem Hyang solved was the 'Gaecheol (開鐵, lid iron)' problem. According to records, after installing the wooden fuse (Mokgok), it was to be covered with a lid iron.
'I don't see any special locking device, so how was it fixed?'
Hyang's question was resolved upon seeing the actual object. The lid portion of the actual Bigyeokjincheonroe was carved in a square shape, and in the center, a round hole for inserting the Mokgok was formed. And the answer lay in that square-carved portion.
The carved portion appeared to be a perfect square but was actually rectangular. And a thick groove was deeply carved into the wall. In other words, after placing the lid iron and turning it 90 degrees, the lid iron would slot into the groove and become fixed. Having solved that one problem, another problem emerged. The hole for inserting gunpowder and pyrites was smaller than expected.
The triangular pyrites shown in various restoration drawings were quite large. In the CG played at the exhibition, they resolved this by inserting pyrites before placing the Mokgok, and inserting only gunpowder through the hole on the side.
'That wouldn't distribute fragments evenly, would it? How peculiar...'
To resolve such questions, Hyang had diligently searched the internet. And one video he found through the internet added more questions.
It was the appearance of Mk.2-1. The video was aired by a broadcaster in the early 2000s.
A professor from a naval research institute appeared, and there they inserted triangular pyrites and gunpowder through the Mokgok insertion hole, then plugged the Mokgok and covered it with Gaecheol. After covering with Gaecheol, they inserted a lead plate into the gap between Bigyeokjincheonroe's body and Gaecheol, then hammered it firmly to fix the lid.
In the subsequent firepower test, Bigyeokjincheonroe poured out fragments from the Gaecheol portion and was left empty. The body of the emptied Bigyeokjincheonroe was almost undamaged.
Ultimately, still unable to resolve his questions, Hyang decided to solve it himself, and the result was the explosion behind the smithy that made his cousin grab him by the collar.
Recalling the tumultuous memories of the 21st century, Hyang, who had been pondering between Mk.1, Mk.2, or Mk.2-1, shook his head vigorously and grabbed his brush.
"Why worry about that? Since I've decided to make it! I'm going with Mk.21! The 21st century version!"
Hyang's choice was to maximize productivity and lethality.
* * *
Watching the ministers discuss etymology, Choi Hae-san opened his mouth.
"This Bigyeokjincheonroe was personally planned and designed by His Highness the Crown Prince."
At Choi Hae-san's explanation, Sejong and the ministers' gazes focused on Hyang. When attention concentrated on him, Hyang spoke confidently.
"Your Majesty will certainly not be disappointed."
At Hyang's words, Sejong responded with a proud expression.
"You have never disappointed this father of yours until now. General, proceed."
"Yes, Your Majesty. First, looking at the structure of Bigyeokjincheonroe, gunpowder is filled inside the explosive shell. When the fuse ignites, it explodes. It appears very simple from the outside, but a very ingenious method is hidden within."
"An ingenious method?"
"The explosion time can be adjusted."
Choi Hae-san explained the usage of Bigyeokjincheonroe.
"Wind the fuse around the Mokgok, insert it into the Jitong, then place it into Bigyeokjincheonroe and seal the lid. Then fill gunpowder through the hole on the side and plug the hole. Afterward, insert it into a Wangu filled with gunpowder and fire it. It will fly 300 paces (approximately 360m) to 500 paces (approximately 600m) and explode."
At Choi Hae-san's explanation, Sejong spoke.
"So the time is adjusted by winding the fuse around that Mokgok?"
"That is correct."
"And its power?"
"I will demonstrate it now. Execute!"
At Choi Hae-san's command, soldiers entered the demonstration ground carrying a large Daewangu and Bigyeokjincheonroe. The soldiers who stopped before Sejong set down everything they had brought and saluted.
"Loyalty!"
The saluting soldiers moved the Daewangu and Bigyeokjincheonroe to the center of the demonstration ground. The Daewangu's muzzle was aimed at an empty lot on Mokmyeoksan Mountain, about 100 jang (approximately 330m) away. At the empty lot, red and blue target boards and scarecrows wearing chainmail, brigandine, and lamellar armor had already been densely set up.
The soldiers who installed the Daewangu prepared the Bigyeokjincheonroe. They inserted the Jitong containing the Mokgok, covered it with a lid, and twisted it firmly with a dedicated tool. Similarly, after filling the hole on the side with gunpowder, they screwed the lid on with the same tool.
Having finished preparing the Bigyeokjincheonroe, the soldiers lifted it and inserted it into the Daewangu. Afterward, the soldiers pulled the Gyeokcheol attached behind the Daewangu, inserted the Donghwamo, then pulled the string attached to the Gyeokcheol and hid behind the protective wall constructed at the rear.
"Your Majesty, please also take cover for a moment. To prevent any unforeseen danger."
"Very well."
At Choi Hae-san's words, Sejong and the ministers hid behind the protective wall installed in front of the stand. Once Sejong was safely covered, the military officer standing beside Choi Hae-san waved a red flag broadly.
"Fire! Fire! Fire!"
Boom! Thwump! KABOOM!
As the soldiers hidden behind the protective wall pulled the string, the Daewangu fired the Bigyeokjincheonroe. Making a whistling flight sound as it crossed the sky, the Bigyeokjincheonroe that landed in the empty lot soon exploded with a tremendous noise.
"Ugh!"
At the explosion and the shockwave that followed, Sejong let out a small groan.
"Your Majesty! What is wrong!"
At Sejong's groan, Hwang Hee, who was right beside him, asked urgently.
At Hwang Hee's question, Sejong waved his hand.
"It is nothing. I was merely startled for a moment."
"Your Majesty, you may rise now."
"Hnn!"
Seeing Sejong rise while putting strength into his thighs, Hyang muttered to himself.
"As expected, he needs to lose some weight... Should I reduce his meal portions?"
Though he muttered in a small voice, Sejong seemed to have heard it and shouted at Hyang.
"You rascal! Are you planning to starve your father!"
"Ah, no! Please look at the targets!"
At Hyang's appearance hurriedly changing the subject, Sejong muttered complaints under his breath and turned his head.
"My goodness..."
Upon turning his head and looking at the target site, Sejong and the ministers could not close their gaping mouths.
Even from a distance, the targets and scarecrows that had been set up around the empty lot were in complete disarray.
"Would you like to go closer and see?"
"We must!"
Seized by curiosity, Sejong took the lead and strode forward.
* * *
"Good heavens..."
"To think this is the power of a single explosive shell..."
The ministers who arrived at the location of the scarecrows could not hide their shock.
Not a single scarecrow remained standing properly. The pillars that had fixed the helmet plates had flown here and there along with the helmet plates, and the scarecrows wearing armor were similarly scattered in all directions.
Sejong and the ministers picked up the fallen target boards and scarecrows to examine their condition.
"My..."
"If these had been real people... I don't even want to think about it."
"If these had been real people... it would have been hell."
Seeing the helmet plates and armor riddled with holes, the ministers shook their heads repeatedly.
As their words suggested, if this had actually been used against people wearing armor, it would certainly have been a terrifying situation one would fear even seeing in dreams.
"If there were survivors in this situation, granting them death might actually be merciful."
Sejong muttered quietly while looking at the helmet plate in his hand. The helmet plate Sejong held had a large hole through which a fist could fit.
Not all ministers showed negative reactions. Jo Mal-saeng, who was in charge of the Ministry of Military Affairs, completely lost his composure.
"Your Highness! Crown Prince Your Highness! Can this explosive shell be mass-produced immediately? No, please answer that it is possible!"
"Well, with just a little effort..."
At Hyang's answer, Jo Mal-saeng immediately prostrated himself fully before Sejong.
"Your Majesty! This explosive shell must be mass-produced immediately! The Jangchongtong and Masangchongtong are also wondrous weapons, but compared to this explosive shell, they are mere trifles!
If only this explosive shell can be mass-produced, the Jurchen problem can be resolved immediately! Not only the Jurchens! Those accursed Tsushima can also be completely subjugated! No, not just Tsushima, we can conquer all the way to the main base of those Wokou!"
"Hmm..."
"Your Majesty! Mass production is absolutely necessary!"
"Hmm..."
At Jo Mal-saeng's desperate shouting, even Sejong's face showed temptation. However, Sejong decided to pause for a moment.
"We have confirmed the power, so let us learn more details before deciding. It may burden Joseon's capabilities."
"Your Majesty! If capabilities are insufficient, then we should increase capabilities! If saltpeter is lacking, we will search every kitchen and privy throughout Joseon; if sulfur is lacking, we will obtain it even through secret trade! If charcoal is lacking, we will cut down every tree in Joseon! Mass production must absolutely proceed!"
Jo Mal-saeng seemed ready to grab even Sejong's trouser legs. At this, Hwang Hee interjected.
"My Lord! Did you not hear His Majesty's royal words! He said we should hear more explanation and then discuss it! What is so urgent! Rise immediately! What an unsightly display!"
"Hnn..."
At Hwang Hee's rebuke, Jo Mal-saeng straightened his body and looked at Sejong. Seeing Jo Mal-saeng's earnest expression as he gazed at Sejong, Hyang muttered inwardly.
'Why does that cat from that movie come to mind?'
* * *
"Explain why Bigyeokjincheonroe demonstrates such power."
"Yes, Your Majesty."
At Sejong's command, Choi Hae-san began his explanation.
—The explosive shell's casing was made as thin as possible. It was designed with strength and thickness to withstand the shock of firing and impact, but not to withstand internal explosion.
—Small iron beads were attached to the inside of the explosive shell casing. These beads increase the number of fragments, enhancing lethality.
—The power of the gunpowder was increased. Though not using Poyu or Deukgap-style gunpowder, the process of mixing soil into Eulsik gunpowder was eliminated to maintain its power.
"Truly, the effort is visible."
At Sejong's evaluation, Choi Hae-san bowed his head and answered.
"The effort was put into adjusting the thickness of the casing. The other parts simply followed what His Highness the Crown Prince had already decided."
Sejong's gaze at Hyang contained many things at Choi Hae-san's answer. Sejong, who had been looking at Hyang like that, asked Choi Hae-san.
"Just now, the Minister of Military Affairs requested mass production of Bigyeokjincheonroe. Is it possible?"
"I believe it would be possible if only sufficient gunpowder is supplied."
At Choi Hae-san's answer, Hwang Hee interjected.
"General, is it truly possible? Earlier, His Highness the Crown Prince mentioned the shortage of craftsmen as the reason mass production of Deukgap-style gunpowder is impossible. Based on what I know, to mass-produce such magnificent explosive shells would require many excellent craftsmen. Wouldn't the same problem arise?"
At Hwang Hee's point, Choi Hae-san nodded.
"Your Lordship's point is correct. However, when His Highness the Crown Prince created this explosive shell, he considered that aspect as well."