"Prepare a few guns, we're going to the range."
Joseph motioned to Martinier, ready to go test the newly completed bulletproof insert, when he heard Eman beside him say, "Your Highness, the King has arrived."
Joseph hurriedly turned around and saw Louis XVI enter the workshop with a proud smile, "Ah, my dear Joseph, I knew I'd find you here inventing something interesting."
Then, he muttered somewhat resentfully, "Why didn't you call me to join you? We're the best of partners.
"Oh, never mind that now, let me see what wonderful thing my genius son has concocted this time..."
However, when he took the bulletproof insert from Joseph, he frowned slightly, "What is this, a piece of iron?"
"This is no simple iron plate," Joseph said as he pulled his father towards the range, "It can withstand gunfire."
Louis XVI weighed the bulletproof insert in his hand, incredulous, "This thing is at most 3 pounds, oh, we've changed to the metric system now, so that would be 1.5 kilograms. It can actually stop bullets?"
As a "tech nerd," he had some knowledge of armor. Even breastplates weighing more than 10 kilograms often got pierced if the bullets' angle of entry was perpendicular.
And yet the Crown Prince thought to stop bullets with such a thin piece!
"You'll see for yourself."
Joseph gave his father a mysterious smile and then ordered the guards to fix the bulletproof insert onto a wooden target, before taking a caplock gun from Martinier—the latest model produced by the Royal Armory, freshly sighted.
Joseph positioned himself 60 paces from the target, cocked the gun, fitted a percussion cap, and squinted at the distant bulletproof insert.
A loud "bang" echoed. He missed the target.
Joseph reloaded awkwardly and fired again.
"Bang!" Still off target.
This was not necessarily due to poor marksmanship; in the era of smoothbore guns, hitting a target 60 paces away often depended largely on luck.
Finally, after the caplock gun fired for the third time, the distant bulletproof insert visibly quivered.
Two soldiers from the range immediately carried the target over at a run.
Louis XVI curiously stepped forward to inspect it and saw that the iron plate had a large dent, but it was obviously not penetrated!
He looked at Joseph in shock, "How is this possible? It's just a thin piece!"
Joseph was not surprised at all; he had set the shooting distance at 60 paces, leaving a considerable margin for error. According to his design, the insert was supposed to withstand shots from a British Brown Bess 1777 Flintlock Gun at 30 paces.
He smiled and removed the bulletproof insert from the target, explaining to his father, "Dear father, in fact this is not just a piece of iron."
He pointed at the insert, which had shown some layering from the huge impact, "You see, behind the iron piece is a ceramic piece."
"Ceramic? Such a fragile thing, what use could it possibly serve?"
"To disperse the impact of the bullets," Joseph said, "You can see from the edge the ceramic has already shattered.
"Since the cracks extend horizontally, they can disperse the vertical impact forces to a horizontal direction."
"Behind that is a layer of silk. Silk is extremely tough; it can wrap around the first two layers, preventing them from being torn apart by sudden deformation."
"As for this last layer of iron, it's to enhance reliability. You see, it only has slight marks on it."
Louis XVI's eyes widened in amazement as he examined the ballistic insert in his hands, nodding continuously, "The simplest structures often have unexpectedly excellent performance. Joseph, how did you come up with this idea? It's simply... miraculous!"
Joseph thought to himself that he had of course seen it on a documentary, but he still followed his usual routine, crossing himself, "I believe, it must be divine inspiration."
Upon hearing this, Louis XVI immediately made the sign of the cross with great piety, "Thanks be to Almighty God!"
In the last two years, with his son continually receiving "divine inspiration," he had become a hundred times more devout than before.
Meanwhile, Joseph said something even more astonishing, "This ballistic insert should still have some margin for error. Let's try again from 50 paces."
A new insert was secured into place. Joseph handed the gun to his father.
As the muzzle belched thick smoke, Louis XVI shot and accurately hit the ballistic insert, then somewhat boastfully raised an eyebrow at his son who had hit the target only after three tries earlier.
The target was quickly brought over by a soldier. Joseph hurried forward to examine the insert; the bullet pit was deeper than before, but it still hadn't been penetrated.
He turned the insert over, and on the underside of the last iron layer there was only a barely noticeable indentation, clearly meaning the wearer would not be in any mortal danger.
This time Louis XVI spoke first without waiting for him, "Perhaps we can try even closer."
As the testing went on, it wasn't until the range was reduced to 28 paces that the ballistic insert was finally penetrated.
Afterward, Louis XVI and his son continued to test several different models of ballistic inserts, falling asleep directly in the armory as night fell, and talked until well past two in the morning about various firearms and mechanical topics.
In the following days, father and son stayed immersed in the armory, conducting a series of tests and improvements on ballistic inserts of all different materials and combinations, and eventually decided on a few types for mass production.
Joseph, looking at the production process documents in his hand, instructed Martinier, "Start with 6000 pieces of the standard type. 2000 pieces of the reinforced type. 500 pieces of the premium type."
Through the days of testing, he discovered that to counter the soft lead bullets of the 18th century, there was no need for double layers of iron."
Thus, following his father's suggestion, he used a structure of iron, cotton, ceramic, and silk to keep the weight of the ballistic insert down to 1.05 kg, able to reliably withstand a shot from a flintlock gun from beyond 40 paces."
This "standard type" ballistic insert was the cheapest, costing only 5 livres and 16 sous. If necessary, even the silk could be omitted, bringing the price down to less than 4 livres, though the effective protective distance would also fall to 55 paces.
The "reinforced type" insert was the structure previously tested, with two iron layers front and back, weighing 1.4 kg, and could only be penetrated by a flintlock gun at a distance of 28 paces, especially designed for Cavalry use. It cost 6 livres and 10 sous.
The "premium type" was a single layer of iron plus double layers of silk, weighing the same as the standard type, with a reliable protective distance of 33 paces. However, its price was as high as 8 livres and 5 sous, usually only available to officers.
In fact, Joseph had originally planned to produce more than 100,000 pieces to equip the entire Guard Corps. However, the bottleneck of adhesives limited his ambitions.
The performance of casein glue was excellent, but at present, it could only be produced in small quantities and was quite expensive. As for other natural adhesives, they were basically useless for large-scale applications.
Joseph recalled the various phenolic adhesives of the future and felt an even stronger desire to promote gas street lamps quickly, thereby illuminating the organic chemical industry.