When Bai Zhizhan visited the "Huaihe" class, the technicians of the shipyard focused on radio proximity shells.

In order to test this new type of ammunition, the Imperial Navy had long since converted an ocean-going cruiser equipped with 130 mm and 80 mm anti-aircraft guns into a test ship, mainly to carry out the necessary modifications of the anti-aircraft guns equipped with them, so that they could directly use radio proximity shells.

As for the test targets, that is, some remotely piloted aircraft.

The results show that the main value of radio proximity shells is reflected in long-range interception.

To put it simply, when the engagement distance is between 5 and 15 kilometers, radio proximity shells can be more effective in intercepting incoming enemy aircraft. The biggest advantage of this is that it forces the enemy aircraft to disperse before entering the attack range, so that it is impossible to launch an organized attack on the aircraft carrier.

This alone is enough for radio proximity shells to gain the favor of the Navy.

According to the statistics made by the Imperial Navy, in the previous battles, almost all the attacks on aircraft carriers came from cluster attacks.

In other words, the threat to the aircraft carrier from enemy aircraft launching a single assault is minimal.

In addition, it is certainly much easier to intercept one enemy aircraft than a group of them.

When the combat distance was shortened to 5 kilometers, the combat efficiency of the 130-mm anti-aircraft guns was greatly reduced because of the insufficient rate of fire, and even if radio close-fire shells were used, the hit rate was not very high. Because the reloading procedure is more complicated, it will reduce combat efficiency.

When the engagement distance is reduced to 3 km, the effectiveness of the 80mm anti-aircraft guns using radio proximity shells is also significantly reduced.

In other words, to deal with approaching enemy aircraft, it is still necessary to rely on 40 mm and 20 mm machine guns to kill and damage enemy aircraft through dense barrages.

It was so that on large cruisers, 80-mm anti-aircraft guns replaced 130-mm anti-aircraft guns.

Substitution, to be precise.

Because of the strong opposition of the officers and men of the fleet, during the construction, the design plan was temporarily modified, and four twin-mounted 130-mm secondary guns were retained, to be precise, Gaoping dual-purpose guns.

It's just that the number of 80-mm anti-aircraft guns increased to 32 guns, that is, 16 twin turrets.

In addition, the number of 40-mm guns reached a staggering 72, with a total of 18 4-pack gun emplacements.

Interestingly, on the contrary, the number of 20-mm guns was reduced by more than half, only 22 guns remained, and in addition, 4 to 8 more could be added as needed.

Here, there is another new type of anti-aircraft weapon that has not yet been officially equipped.

In actual combat, the Imperial Navy discovered early on that in close air defense operations, accuracy and power are not as important as the rate of fire.

Most of the time, it is actually relying on barrage to intercept enemy aircraft.

There's only one point: in the heat of battle, even the best gunners are nervous, and their reaction speed may not be able to keep up.

Most of the time, the gunner actually aimed roughly, that is, opened fire as soon as he spotted the enemy aircraft.

As for aiming, that was after firing.

As a result, anti-aircraft guns had to have a sufficiently high rate of fire.

Herein lies the problem.

Increasing the rate of fire of anti-aircraft guns is not an ordinary difficulty.

A small-caliber anti-aircraft gun like the 20 mm is a little easier to handle, as long as the problem of ammunition supply is solved, and then the heavier barrel is used, it can reach a rate of fire of more than 600 rounds per minute, and the continuous firing time is more than 10 seconds, which is enough in actual combat.

It's just that if the caliber is larger, the problem will become very complicated.

For example, the 40-mm anti-aircraft guns that are widely equipped with the navies of various countries limit the rate of fire, in fact, it is not that the barrel is overheated, but that the shells are too heavy and the ammunition supply mechanism cannot keep up!

The traditional solution was simple and crude, that is, several anti-aircraft guns were installed in parallel, and the density of fire was increased by increasing the number of anti-aircraft guns.

Quadruple is already standard, and the Royal Navy even has an eight-pack version!

It's just that this doesn't solve the problem at the root.

The point is, space on a battleship is precious.

The Imperial Navy's quadruple 40-mm anti-aircraft guns occupy about the same deck area as the twin 80-mm anti-aircraft guns, equivalent to 70 percent of the twin 130-mm anti-aircraft guns, and the total weight of the system reaches 20 tons, so its range of use and the number of equipment are strictly limited.

Even fast battleships were equipped with about 60 quadruple 40-mm anti-aircraft guns.

No matter how much it is, not only will there be no place to install it, but it will also cause the center of gravity of the battleship to rise.

It is because they are too big and heavy that many destroyers built before the war use a twin version, not a quadruple version.

For small-caliber anti-aircraft guns, overheating of the barrel remains the number one problem.

Take the Imperial Navy's 20mm anti-aircraft guns as an example, the latest model has a design rate of fire of 900 rounds per minute, but the combat rate of fire is less than 150 rounds per minute, mainly because when firing continuously, the barrel will quickly overheat, so it can only be fired in short bursts.

As for the multi-pack 20-mm guns, there is little point.

The reason is also very simple, when the 20mm machine gun came out, it was actually used to replace the 13mm heavy machine gun, and the firing range and firing height were very limited.

In real combat, the main value of the 20-mm cannon is to deal with fish that slip through the net.

Crucially, turret deployment occupies a large deck area, and gun emplacement does not have this problem.

It was in this way that the Imperial Navy came up with the idea of increasing the rate of fire by increasing the number of barrels.

If anything, it is a machine gun that uses the Gatling principle.

However, because it is too complicated, and the operation control is also very troublesome, it cannot be controlled by manpower, and even cannot be aimed by the gunner, it must be driven by hydraulic or electrical power, and it must be equipped with optically assisted aiming equipment, and the curb weight is very high, so it is very difficult to develop.

Long before the outbreak of the Great War, the Imperial Navy began to develop the Gatling cannon.

Originally, the principle of internal power was used, that is, the gunpowder gas produced when the shell was fired to drive the barrel, and no external power supply was required.

After completing the conceptual design, the Imperial Navy abandoned this more achievable scheme and opted for the more difficult external power mode. The motor drives the barrel to rotate and complete a series of actions such as loading, firing and unloading, so as to control the rate of fire more effectively.

Because it is too difficult to develop, so far there are only a few sample guns.

The most critical issue remains miniaturization.

According to the introduction, the lightest set of the trial production of those prototypes weighed 12 tons, and it occupied an area equivalent to a quadruple 40-mm anti-aircraft gun. With the same mass, and the same deck area, more than 10 20-mm guns can be deployed intensively.

Obviously, the combat efficiency of a set of Gatling guns is certainly not comparable to that of more than 10 20-mm guns.

In addition, the 20-mm shells were indeed a little worse, not only in terms of short range and high firing range, but also in terms of their damage to aircraft. Especially against large aircraft, such as heavy bombers, 20 mm shells often cannot achieve the effect of destroying one or several rounds.

In addition, reliability is a big issue.

According to the technical personnel, as long as the reliability problem is solved and the curb weight is reduced by about 30%, there will be a way to obtain procurement from the Navy.

If you can, you might choose a new caliber, such as 30 mm between 20 mm and 40 mm.

By that time, I'm afraid there will be only two caliber anti-aircraft guns.

It's just that when that day will come, no one knows.