[slugmensch]

Sorry, gentlemen, but I must take issue with those that claim that the "ribs" on the foster slugs are to impart spin - this does not happen (it has been proven not to work in tests with high-speed photography). The companies which manufacture slugs with the ribs in a helical pattern are only wishing - or perhaps they do it for looks - but they impart no real stabilizing influence. The ribs are not designed to reduce contact area (to reduce friction), either. The purpose of the ribs is so that, if one was to fire such a slug through a barrel with some amount of choke - the lead would have a place to "flow" as the slug deforms through the choke - rather than potentially splitting the end of the barrel. The name commonly applied to foster - type slugs (i.e., "rifled" slugs) is a total misnomer.