An interesting note about the Foster-style "rifled" slugs. Most folks assume the spiraled lead projections on these slugs are intended to impart a spin, but any spin they create is purely incidental. As already mentioned, the nose-heavy "shuttlecock" design is the source of the slug's stability; the "rifling" projections simply allow a slug to be centered in the bore, yet safely compress and exit through a choke without causing damage. Cylinder bore is usually recommended for slugs, but Foster slugs can be safely fired even through a full choke, and accuracy with some choke can sometimes be very impressive.

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Pisgah