According to this article at Popular Science, a team of Chinese scientists say they should be able to create nuclear fusion by firing a bullet made of diamond into a block of crystal methane. Note: this is not the crystal meth that is so popular around here.
Catch is, that bullet would have to be shot at about 3,280,840 fps or about 746x faster than my .22-250 shoots. The bullet would be 1 cubic mm volume. So at 0.00352 g/mm^3 that bullet would weigh 0.054 grains. Or 1/740 of the weight of my .22-250 bullets. But due to velocity’s role in the calculations, I get that the muzzle energy firing that tiny little bullet would be about 734x the muzzle energy of my .22-250. In other words, good luck with that guys. And let me come watch when you do it!