Originally Posted by
Vorpalis
Coatings can have the same types of issues, but because coatings generally have far less mass than the jacket or core (even molybdenum-based coatings), those issues have far less of an effect. If a coating had enough mass, then it could cause instability and accuracy issues.
Think of a bullet spinning around its long axis like spinning a wooden top. If the top is out-of-round -- like tolerance stacking with a bullet's core and jacket -- it will begin wobbling almost immediately and crash. If you start with a perfectly round top, then apply caulking unevenly around the outer edge, it will wobble and crash, despite being perfectly round, because caulking has enough mass relative to the wooden top. However, if you take that perfectly round top and instead apply a wood stain, that isn't going to have a significant effect on the top no matter how unevenly you apply it, because it just doesn't have enough mass relative to the mass of the top.
Fun fact: the Earth's lack of radial symmetry -- more water in one place, thicker crust in another -- is why Earth wobbles on its axis. In fact, the earthquake in Tōhoku (Fukushima) Japan back in 2011 shifted so much of Earth's mass that it permanently changed Earth's rotation, shortening the length of every day from then on by 1.8 microseconds.