After the collapse of the USSR the media started reporting on a mysterious weapon developed in the 1960s. Nobody really knows whether it was a hoax, or the “nuclear bullets” really existed.
Nuclear machine gun
The main material for creating a nuclear bomb is either uranium-235 or plutonium-239. In order for explosion to happen, the charge should have critical mass. The critical mass of uranium and plutonium is 1 kilogram. The nuclear ammo’s caliber for heavy machine guns was reported to be 14.3mm and 12.7mm. Some even reported 7.62mm caliber nuclear bullets for Kalashnikov assault rifles. Such small nuclear projectiles are widely considered to be unlikely even today.
According to the sources, Soviet physicists were producing the nuclear bullet fillers out of transuranium element called californium. The atomic mass of this element is 252, while its critical mass is meager 1.8 gramm. Californium-252’s biggest advantage, however, is that from five to eight neutrons are created during its fission, as opposed to uranium and plutonium creating from two to three.
The scientists have figured out two ways to produce californium. The first one is considered to be the simple one — a nuclear bomb explosion. The second one is to create the isotopes using a nuclear reactor. The former method is considered to be more effective, because the fluence rate of neutrons is superior compared to producing californium in a reactor. However, you’d have to conduct nuclear tests non-stop. They were apparently conducted at the inf
amous Semipalatinsk Test Site.
So, the bullet had a tiny californium part not heavier than 6 gramm in a form of a dumbbell — two hemispheres connected by a thin bridge. The explosive in the shell was in a form of a compact ball 8mm in diameter (in the case of a 7.62mm bullet). These were enough to produce a nuclear explosion upon impact. The tests reportedly showed that one bullet was able to smelt tank armor and vaporize bricks.