Do not see the knowledge of bulletproof helmets
About the aramid helmet (Kevlar is the commercial name of aramid 1414) bulletproof ability, 1985 PASGT helmet equipped with the U.S. Army has reached NIJ ⅢA level of protection, can resist shrapnel, rifle rounds of stray bullets, ordinary pistol rounds / shotgun pellets of direct fire at close range, and this "resist" is including what some people call "impact"; and China's successful research and development in the 1990s QGF02 helmet should also be this level, tested at a distance of 5 meters to 54 pistols fired 51 type ordinary bullet vertical incidence rate of 100%. It is worth mentioning that the protection of metal helmets may not be weak chick. Called the "strongest helmet of the alloy era" of the East German M56 helmet, at a distance of 15 meters by 9mm Parabellum pistol rounds and 7.62mm Tokarev pistol rounds direct fire, no penetration, no cracks; and because the suspension system design is excellent, can effectively reduce the secondary damage caused by helmet deformation.
At present, the helmets in service in various countries are also basically NIJ ⅢA level of protection. Helmets that can withstand direct fire from rifle rounds of intermediate power are being developed by countries (the United States, Israel, etc.), but most are not yet practical. U.S. "enhanced combat helmet" (ECH) from 2007 began to develop, can withstand AKM assault rifle close range direct fire, after 2013 gradually adopted by the U.S. Marine Corps and the U.S. Army. In fact, the helmet to protect the middle power rifle bullet direct fire is not difficult, the difficult part is to control the weight.
In June or July 2020, the ECH helmet was tested in the photo, should be 7.62x39mm rifle rounds hit. ECH helmets can protect the M43 rifle ammunition is 7.62x39mm specifications, the kinetic energy out of the chamber is two thousand joules out of the head; and World War II U.S. .30-06 rifle ammunition is 7.62x63mm specifications, the kinetic energy out of the chamber is close to Four thousand joules.
About the "suspension system" of modern helmets
A .357 Magnum warhead weighing 10g hits a smallest PASGT helmet (1.4kg) at 450m/s, with the warhead embedded in the helmet body, both moving together at only 3.2m/s, or about 11.2km/h, equivalent to a head-on collision with a tree wrapped in hard foam while jogging along. If this can also cervical fracture, it must be the parents of the child's cervical spine caused by the tofu-dreg project. Rifle ammunition is also impossible to fracture the cervical spine, even a full-power rifle ammunition with a 9.5g warhead and 840m/s muzzle velocity like 7.62x51mm NATO cannot do it. Assumptions (hypothetical!) The helmet material can be guaranteed not to be shot through, and the helmet and warhead are moving together at a speed of only 5.7m/s, or 20.5km/h, equivalent to riding a bicycle into a tree wrapped in hard foam. In fact, hitting a tree or wall at that speed is more injurious than actually being hit by an accelerated helmet, because the helmet is only 1.4kg, while the human mass is much larger. A more appropriate example should be, was wrapped in a sponge half of the brick shot, which will be how much injury? A little dizzy is inevitable, the back of the head cold slapped also have to faint a while.