China has finally adopted a 9mm submachine gun for police that replaced the 7.62x25 pistol round developed by Russia but used mainly by Russia. The rest of the world adopted the 9x19 Parabellum pistol round early but Russia, then China, kept the 7.62x25 round going for decades.
The new Chinese submachine gun is the JH16-1, a more modern design than the Type 79 (introduced in 1983) using the 7.62x25. The Type 79 was lighter (1.75 kg/3.9 pounds) and had a higher rate of fire (16 rounds a second). The JH16-1 weighs 2.8 kg (6.2 pounds) and has a rate of fire (13 rounds a second) that is more suitable for police work. The heavier is a steadier firing platform and more sturdy in general.
Even before World War II the 9mm round was displacing the 7.62x25 and despite the success of the 7.62x25 Tokarev during World War II (as a pistol and submachinegun round) it was used mainly by the Russians and was eventually displaced by the universally popular 9x19 Parabellum round. With China adopting a 9mm submachine gun, in addition to the 9mm pistols long used by Chinese soldiers and police, the 7.62x25 has become even more of a niche round. That said, both 7.62mm 9mm pistol rounds have their good qualities, something that should not be overlooked.
Equipping infantry (and later police) with lightweight automatic weapons began with German innovations during World War I. In doing that, the Germans also took the lead in developing submachineguns, like the MP 18, a weapon that would eventually evolve into the modern assault rifle as well as numerous 9mm automatic weapons for police. By the end of World War I, about 30,000 MP 18s were in use. The MP 18 demonstrated the devastating effect of automatic weapons in the hands of infantry. The MP 18 fired the standard 9mm pistol round at the rate of 6-7 bullets a second and used a 32 round drum magazine. The basic need was for a compact weapon that could quickly fire a lot of bullets. This gave the MP18 user a big edge in combat. The Germans kept developing this type of weapon and by World War II they had the MP 38 and MP 40. The short range (50-100 meters) of the 9mm pistol round prevented the Germans from attempting to rearm all their infantry with this weapon because the troops often had to hit targets farther away.
It wasn't until they saw the Russians use similar weapons on a mass scale during World War II that the Germans realized that the short range of the 9mm pistol round was not as great a shortcoming as they thought. The Russians understood that for an attack, arming all the troops with submachineguns gave you so much firepower that the enemy had a hard time shooting back at your advancing infantry. This was particularly useful in urban or trench warfare, where there were a lot of small-scale (a dozen or fewer attacking troops) operations at short ranges.
Russia produced over five million of their 3.6 kg (8 pound) PPSh 7.62x25 submachineguns. It used either a 35 pound box magazine (weighing 680 grams/1.5 pounds) or a four pound drum holding 71 rounds. That was 7-8 seconds worth of firing. The bullet used was a 7.62mm (.30 caliber) pistol round that moved at only about 516 meters (1,600 feet) per second. Catch one of these in the head, and you were dead. Anywhere else, and you would probably live. But with so many of these bullets flying around, multiple hits were more likely and that is what made the PPSh Russian troops so effective. .
One thing the 7.62/25 PPSh round didn't have was penetration, at least compared to rifle bullets. You needed that in urban areas to fire through doors, floors and walls. The Germans overcame this by developing the StG-44 in 1943, which used a more powerful, 7.92mm, bullet. This weapon heavily influenced the design of the AK-47. The StG.44, like the AK-47, used a shorter (than the standard rifle), and about 20 percent lighter, a cartridge that used a bullet that could still fire through walls and doors. The Russians combined the best features of the StG-44 and PPSh to produce the AK-47 after World War II. It was cheap, rugged, used a larger, more powerful bullet, and enabled green troops to generate a lot of firepower on the battlefield.
Even before World War II the 7.62x25 pistol round was losing out to the more compact, slower moving 9x19 round. Both were developed in Germany. The 7.62x25 pistol round came first in the 1890s and was simply a shorter, much less powerful, rifle cartridge. While popular it was largely displaced in 1902 with the development of the 9x19 round. The 9mm round was shorter, had less of a kick (less propellant) and allowed for the design of more compact and easier to handle pistols. The Russians developed a more powerful 7.62x25 round that had more propellant, higher velocity and used steel core bullets (that had more penetration.) This 7.62x25 Tokarev could fit in pistols using the less powerful 7.62x25 round but was not safe to use that way. A weapon had to be sturdy enough to handle the 7.62x25 Tokarev safely. Any pistol firing the Tokarev round was heavier and had quite a recoil compared to 9mm ammo. Meanwhile, the 7.62x25 Tokarev was outstanding in Russian submachineguns. Despite its larger (longer) size and greater kick, the 7.62x25 Tokarev continued to be popular as a pistol round in some parts of the world. For what it’s worth the fictional MI6 agent James Bond preferred the original 7.62x17 ammo fired from his compact German PPK pistol.