The Later Jin army withdrew from Tongzhou and headed straight for Liangxiang. On the one hand, it was related to Huang Taiji's own idea that he could not conquer Tongzhou. On the other hand, the Later Jin army went deep into the Ming territory and relied on the Ming army that they did not dare to fight with the Jin army. Even if there were only a few hundred people, they could walk sideways within the Ming territory. Only then did the Later Jin army dare to act so recklessly. However, this time, the Later Jin army was bleeding under the city of Tongzhou, and had suffered several losses in Li Laoer's hands before, which greatly boosted the morale of the Ming army and gained confidence.

If the Later Jin army had been in Tongzhou for a long time, once the Ming army such as Yuan Chonghuan, Man Gui, Mo Yunlong, Ma Dengyun, Sun Zushou gathered and came to Tongzhou, Sun Chengzong would then come out of the city and cooperate with the outside, the Later Jin army might suffer a crushing defeat at Tongzhou.

Therefore, Huang Taiji's retreat was very rational.

Li Laoer read a history of the Qing Dynasty, which was about the battle between the Ming army and the Later Jin army outside Yongding Gate: Man Gui, Mo Yunlong and Ma Dengyun, and the four generals of Sun Zushou led 40,000 horses and infantry, and built wood, and arranged guns and cannons on all sides. The soldiers fired guns and cannons like rain and snow. No one of our army was dead when they attacked. Isn’t it God bless?

That was because the Ming army's firearms were of poor quality and could not penetrate the shield chariot of the Later Jin army. The Later Jin army used shield chariots to protect the white-armored soldiers from approaching. After getting close, they shot with bows and arrows almost close to their faces, and then used white-armored soldiers to break the formation.

Even a general like Man Gui is hard to match against a few white-armored soldiers.

Li Laoer was able to repel the Later Jin army in Tongzhou, on the one hand, the Ming army in Tongzhou was strong, and on the other hand, Li Laoer's defense line was arranged very reasonably, with trenches and earthen walls and wooden fences tied on the earthen walls. It was almost as difficult for the Later Jin army to attack such positions as siege.

After the Later Jin army withdrew, Sun Chengzong ordered Li Laoer to continue to help him build a snowmobile camp, preparing to wait for the snowmobile camp to form a scale, and send the car camp to Beijing to serve the king.

Li Laoer was unable to make a flintlock rifle due to the low quality of the Daming Firearm. He knew how to build a flintlock rifle, and he knew how to cast a bird gun, and he knew how to cast a three-eyed gun, but casting a cannon requires a lot of money. Sun Chengzong did not have that much silver at hand, and he lacked enough pig iron. In addition, Li Laoer did not know how to make fine steel to make springs for flintlock rifles. Without high-quality springs, flintlock rifles could not be made.

Through the observation of the Ming army's Shenji Camp during this period, Li Laoer discovered a problem: except for the 3,000 kilograms of red barbarian cannons and about 1,000 kilograms of general cannons, the other cannons were so-called medium-sized enemy-killing cannons below 100 kilograms, medium-sized Folang, light Folang and tiger squat cannons.

The two so-called medium-sized artillery, the Imperial Cannon and the Medium-Sized Folang Machine, are both cannons of about 100 kilograms, while the light Folang Machine and the Tiger Squat Cannon are small cannons with only a few dozen kilograms.

The so-called large Folang machine cannon of the Ming army weighed 300 kilograms and could only fire projectiles of about one kilogram. The field cannons of the same weight in Europe could fire three pounds of shells.

This is because the weight of the projectiles that the Fran cannon can fire is only half of the weight of the front-loaded projectiles at most. A three hundred kilogram field gun can fire three pounds of shells. The Fran cannon can reduce at least half, which means that it can only fire about one kilogram of shells. For safety reasons, it can only fire one kilogram of shells.

The weight of the pound is heavier, and one pound is almost equal to 15 pounds.

In other words, a 300-pound "heavy Folang Machine" cannon fired at one time could not destroy a shield car of the Later Jin army!

To destroy a shield car, according to Li Laoer's calculations, it is necessary to have a cannon of more than three pounds of cannons. However, Li Laoer would not consider the thousand-jin General Cannon and the three-jin Folang machine cannon. Those cannons are too bulky and are not suitable for field cannons.

From this data, we can see that the Ming army did not have medium-sized field artillery weighing 300 to 5000 kilograms at that time. Only these types of artillery can be truly called medium-sized artillery. The so-called medium-sized artillery of the Ming army actually belongs to the scope of light artillery.

After observation, Li Laoer found that the Ming army preferred the Flang machine cannon because the Flang machine cannon was loading fast. However, the fast loading speed was achieved by sacrificing the pressure of the cannon chamber, which created the disadvantage of the Flang machine cannon insufficient power.

According to the pressure of the artillery that year, Li Laoer looked through artillery information in his previous life, which was about 100 megapas. The conversion result was that he had to bear one ton of pressure per square centimeter.

Let’s look at the Fran machine cannon. Most of the chamber pressure is subjected to the sub-gun. How much chamber pressure can the thin tube wall of the sub-gun withstand? So it can only reduce the amount of gunpowder loading, which means that the power must be sacrificed for rapid loading.

If the Fran machine cannon can destroy the shield of the Later Jin army, it would require a thousand-jin Folang machine, and the thousand-jin Folang machine could only fire six-pound shells, which was far less powerful than the general cannon. If the loading speed was fast, the loading speed of the thousand-jin Folang machine would not be much faster. The weight of a sub-gun must reach 100 jin. Although the loading speed was a little faster than the thousand-jin Magun gun, the power was reduced too much.

In response to the insufficient power of the Folang machine, Li Laoer first considered transforming the sub-gun. If the pipe wall of the sub-gun is thickened, it will increase the weight and affect the loading speed. If an iron hoop is placed outside the sub-gun, the sub-gun cannot be placed in the belly of the cannon. So Li Laoer thought of a wonderful method: to make an iron-core copper-shelled sub-gun, with a cast iron core and a copper shell on the outside, so that it can increase the chamber pressure that the sub-gun can withstand. In addition, inserting the front section of the copper shell into the cannon barrel can increase the air tightness of the Folang machine gun and the sub-gun and reduce air leakage.

In the Tongzhou Blacksmith Workshop, Li Laoer directed the craftsmen to shrink the sub-gun of the 100-jin Folang machine and cast a sub-gun.

"This gun has shrunk a lot!"

"Is the wall of the pipe too thin? Will it explode if it is so thin? "

"Not to mention the explosion, if this thing is put into the belly of the cannon, I'm afraid the gunpowder gas will leak out?"

The craftsmen were talking about it, and they all felt that the gun was useless.

But then, Li Laoer asked someone to cast a copper tube that was slightly larger than the core of the Zi Gun and was longer than the length of the Zi Gun. After casting, while the temperature of the copper tube had not completely decreased, he clamped it with pliers and put it on the core of the Zi Gun. When the copper shell cooled down, the copper shell tightly wrapped the core due to thermal expansion and contraction, thus creating a copper shell iron core.

According to Li Laoer's guidance, the craftsmen loaded gunpowder and projectiles into the gun. Originally, the 100-jin Folang machine cannon projectiles weighed 5 taels of 9 cents and were loaded with 5 taels of medicine. After Li Laoer's improved slaughter, the craftsmen loaded seven taels of medicine.

"Okay, you can test the shooting." Li Laoer ordered the craftsmen to test the shooting of this Folang machine cannon.

Because the charge of nearly 50% of the charge was increased, the craftsman in charge of fire fire held a torch in his hand and trembledly lit the fuse inserted on the fire door. After igniting it, he threw the torch down and ran away quickly, fearing that the chamber would explode.
Chapter completed!