Four days later, the backyard of the North Slope Mine Burning Room.

Two deep holes were dug in the ground in the courtyard, each of which was circular in shape, narrow at the top and wide at the bottom. The inner diameter of the anterior section is about 20 cm, and the inner diameter of the posterior end expands to 26 cm. The inner walls of the holes had been baked by Anna, and the top layer of the earth had been sintered into a single piece, as if a shell had been attached to it. The chamber is facing down to achieve better wall quality when casting, and the higher it goes, the more scum and bubbles it contains. The size of all the caves was calculated from cannonballs, and he roughly remembered that the so-called six-pounder guns and eight-pounder guns were named after the weight of the cannonballs, so he poured out several twelve-pound iron balls, and then calculated the inner diameter of the mold according to the diameter of the iron balls and the thickness of the barrel wall.

In the absence of measuring tools, Roland simply customized the standard, he cut a piece of iron about the width of his ring fingernail and set it as a basic unit, one centimeter, and then used it to make other sizes of iron bars, and engraved the segmented lines.

The diameter of the twelve-pound iron ball was about twelve centimeters under the crude iron ruler, and he set the thickness of the pipe wall at the thinnest point to four centimeters, and the wall thickness was expanded to seven centimeters at the rear end of the chamber to prevent explosions, so as to obtain the inner diameter of the mold. As for the length, although he knew that the artillery had a double diameter, he was only impressed by the double diameter of the main gun of the battleship and the main station tank, and as for the antique front-loading gun, he really didn't know.

Considering that the shorter the body tube, the lighter the weight, and the more material saving, Roland waved his hand and took the value of one meter five. If you are not satisfied with the test firing effect, you can adjust it later.

When artillery was first invented, it was made of a wooden core with iron bars and iron powder, reinforced with iron hoops, and finally burned off the core material in the barrel, like a storage barrel. Of course, Roland knew that this kind of gun was prone to air leakage and explosion of the chamber, so he directly adopted the process of integral casting and boring machine drilling. For a steam boring machine, whether it is a six-pounder gun or a twelve-pounder gun, there is no essential difference in difficulty.

In line with the idea that caliber is justice, he naturally chose a twelve-pounder gun with a larger muzzle and a thicker barrel. Further up, it is not easy to use as a field gun. As for whether the weight of the shell is calculated in lead ball or iron ball, it does not matter, as long as it can be shot. After all, he is borrowing from history, not playing with copy models.

"Let's get started," Roland said to Anna with a deep breath. The latter nodded, grabbed a steel ingot, and dangled it over the hole. The green flame ignited, and the ingots quickly turned red, then melted, forming a small waterfall of molten steel that flowed into the hole. The surface of the molten steel is reddish-orange, and the inner core turns incandescent, making it difficult to see directly. In order to protect the witch's eyesight, Roland also deliberately set up a support at the entrance of the cave, she only needed to determine the position in advance, leaned her arm on the support pad, and did not have to stare at the molten steel to see if it flowed into the hole.

These ingots are slowly accumulated, and Anna alone cannot start the era of large-scale steelmaking, but small batch production is not a problem for her - after the most difficult temperature level is solved, the steel can be fried to obtain better quality steel.

This is also the reason why Roland dared to customize the size of the barrel. Compared to pig iron barrels and bronze barrels, steel cast barrels obviously have higher strength. Even if the size is not right, the gun will not blow up easily.

The molten steel is gradually rising, and the number of steel ingots saved is also decreasing rapidly, which makes Roland feel a little heartbroken. When will he be able to build a pile of chimneys and blast furnaces on his territory to smelt an inexhaustible supply of steel? For a long time, steel production was one of the yardsticks of the strength of the great powers, and he now felt it firsthand.

Filling the two molds, Anna's cheeks turned red. Roland pulled out a handkerchief and gently wiped the sweat from the tip of her nose. At first, Anna would show some resistance, but now she obediently remained motionless, closing her eyes and letting Roland do it.

The dangling bangs are dyed red under the molten steel, and the soft neck makes people want to take a bite. When you are condescending, the other person's half-slender collarbone exposed through the collar will come into your field of vision. When I got closer, I could still smell the faint fragrance coming from her.

"Ahem, it's okay......" Roland put away his handkerchief and retracted his emotions at the same time, "Let's stop here today." Well done, I'll instruct the kitchen to reward you with an extra black pepper steak for dinner. ”

Not yet, he thought, and doing so would inevitably lead to the suspicion of taking advantage of others' danger. Wait until she is truly free......

Anna opened her eyes, and although the sweat had been wiped away, her face seemed to be redder than before. She nodded at Roland and whispered yes.

Over the next few days, Roland traveled back and forth between the castle and the North Slope mines.

In addition to the barrel, he needed to make a sufficient amount of boring knives.

This tool for drilling is similar to the barrel of a cannonball, with the exact same diameter as a cannonball, and after it is removed from the mold, Anna heats it up again and forms it with a hammer. It is very different from ordinary spiral knives in appearance, and at first glance it looks like a blunt-tipped iron bar. The only difference is a notch in the top of the head that is used to expel metal debris. Finally, it is quenched to improve the hardness of the boring cutter.

Unlike the high-precision drill bits of modern boring machines, Roland only needed an iron rod that could make a hole, and he and Anna made five simple boring tools in a week, taking into account the high wear rate. Prior to this, the steam boring machine had already proven its capabilities – the production of pig iron barrels increased rapidly from two per month to ten per day.

When everything was ready, the blast embryos were dug out of the pit by the miners, cleaned of the scum from the surface, and loaded onto a wagon to be transported to the blacksmith's shop.

These two cannon embryos have almost consumed the steel that Roland has accumulated, and it is not an exaggeration to say that they are priceless. During the transport, the prince ordered Carter and two knights to guard the whole process, which made the chief knight feel that this was a bit of a superfluous move. Who would steal something so dead?

The blacksmiths leveled and polished the surface of the cannon embryo at the prince's request, and after polishing the grinding stone, it was sent to the castle's backyard without stopping. At this time, the two round solid steel rods have a dark gray appearance, exuding a thick metallic luster.

Roland couldn't wait to replace the boring cutter and worked with Carter to secure the blast blank in place so that the tip of the cutter head was right in the center of the rod.

Faced with this historic moment, Roland pulled down the valve of the steam engine. The boring tool starts running slowly, and it doesn't take long for it to rise to a steady speed.

"Knife in!" shouted the prince.

The Chief Knight pushed the sliding base to control the depth of contact between the blast blank and the boring tool, and when the blade touched the barrel, the screeching noise suddenly drowned out the roar of the steam engine. The lard, which acts as a lubricant, is squeezed into the borehole, and what emerges is black foam and curly wire. The onlookers withdrew from the hut, but Lightning was the only one who remained where she was. It seemed to her that these swarthy machines were more beautiful than any view.