Tungsten alloy hollow projectile cartridge is an incoming expansion projectile. Its warhead has a fully perforated hole in the center. The aim is to use air to stabilize the warhead. As its center is opened, air resistance decreases and its initial velocity is a little higher than that of similar single head projectiles. It has the characteristics of low penetration and high stop. When it enters the human body, it will expand into the shape of "mushroom head".
Tungsten alloy hollow projectile cartridge is commonly used as handgun projectiles. After the bullet is hollow, the killing power increases, it is easy to roll in the human body, and it is very safe. After a few tens of meters, the speed attenuates to no killing power, and it is not easy to hurt irrelevant people, so the police often use it.
More details, please visit:
http://www.tungsten-alloy.com/en/alloy04.htm