Do Rifled Foster Slugs REALLY spin or it is just a MYTH?

Sometimes the information we have about things is accepted without ANY question. We have been told that the rifling on a Foster slug is just there for “cosmetic” reasons and the slugs do not actually spin. Even Field & Steam has told us that “rifled slugs aren’t really rifled”. How could these experts be wrong? Probably because no one has taken the time to actually film them with a high speed camera. Until now. Ask a buddy who likes to cite information from Wikipedia or other websites if a Foster slugs spins, and you can probably win a bet! SEEING is believing!