In fact, small caliber guns with relatively low technical content can be built in medium-sized countries or above in the world, and a simple mortar or rocket launcher can be made with just a few steel pipes. The 20-type 82mm mortar mass-produced during the Anti-Japanese War is not such a product, and so is the cottage 107 rocket launcher mass-produced by guerrillas in the Middle East. It is difficult to manufacture large caliber and high precision artillery. There are only a handful of countries with this level of artillery manufacturing technology. Except P5, Germany, Sweden, Austria and South Africa all have complete technology. Japan and South Korea all imported semi-finished technology from Germany, while Turkey and India imported semi-finished technology from Korean K9 artillery. Can you imagine their level? Without your own technology, you can only buy it. I was cheated when I bought it. For example, India does not have its own practical mountain guns and dreams of becoming the hegemon of South Asia. Then you can only buy a single M777 howitzer from the United States for more than 5 million dollars, and you can only swallow it by crushing your teeth. So why is it so difficult to make large caliber guns?

(M777 was bombed as soon as it arrived in India)

The barrel is the crown work of modern metallurgy and metal processing industry.

We often say that aero-engine is the flower of industry, and the manufacturing of gun barrel is no less difficult than that of industry. At the moment of propellant explosion, the barrel has to bear high temperature above 3000℃ and high pressure above 800Mpa, and it is also ravaged by high-speed projectile rotation friction. Therefore, the gun barrel must have high temperature resistance, friction resistance, high strength and high toughness, and to achieve this requirement, it must have excellent alloy steel. The modern mainstream gun barrel generally adopts carbon-nickel-chromium-molybdenum-vanadium alloy steel. During the blockade period of the last century, China also developed a series of vanadium alloy steel substitutes, and the element ratio and smelting process of this rare element alloy steel are almost top secret of all countries, which shows that it is very difficult to develop, and this item excludes 80% of the countries in the world.

With the right steel, this is only the first step. After processing into barrel blank, you have to use electroslag remelting to remove phosphorus and sulfur, further improving the strength and life of steel. This technology has also been monopolized by the five permanent members and Germany, Austria, Sweden and other countries, which is highly coincident with the manufacturing countries of large-caliber artillery. At present, the world's largest 450-ton electroslag furnace is developed and produced by Shanghai Heavy Machinery Group, which reflects to some extent why China can now become one of the strongest artillery producers in the world.