I can upgrade the shelter

The two twin-mounted Maxim machine guns have been installed, and after the upgrade, the gate looks thicker and sturdier.

Especially since the gate’s structure was changed from sliding to lifting, the entire gate is now neatly embedded in the wall. To open it without lowering the gate, one would have to blow up the entire wall.

The original gate, made of ordinary steel-plated reinforced concrete, was upgraded to solid heat-treated homogeneous nickel-chromium alloy steel plates with a thickness of 30 cm.

During World War II, Japan used this type of steel as the main armor for the Yamato-class battleships and stacked its thickness to an insane 650 mm.

At that time, the Yamato-class main gun armor was 650 mm thick, and no cannon could penetrate it in the immune zone.

In fact, the Federation found a piece of this kind of steel after the war. To test its performance, they used the 410mm main gun of a Missouri-class battleship to perform a zero-angle bombardment at a distance of 300 meters to pierce such a steel plate.

However, nearly a century-old technology has turned nickel alloy steel into a common material easily available at steel markets, and it is relatively cheap.

Chen Xin’s previously collected materials included a batch of nickel alloy steel columns, sold as raw materials for metal processing.

In Chen Xin’s original plan, these materials were used not only to reinforce the gate but also to strengthen the internal structure of the shelter.

Of course, Chen Xin’s original plan did not intend to make the gate into a 30 cm thick solid metal door. A hollow structure with a few centimeters of steel plate and reinforced concrete inside would have sufficed.

But after Ding Ning gave him that note, an inexplicable sense of crisis made Chen Xin choose to make the gate solid metal, even though this doubled the survival points spent on the upgrade.

Now, although Chen Xin’s gate isn’t as ridiculously thick as the Yamato-class battleship’s main gun armor, his enemies also don’t have battleship main guns.