What are slugs and how are they different from pellets?

A slug is a solid, bullet-shaped projectile with no diabolo waist or hollow skirt.

Slugs are denser and longer than pellets, have higher ballistic coefficients, and retain energy and accuracy at extended ranges (often 100 yards or more). They require a fast-twist barrel (typical 1:16 to 1:20) to spin-stabilize them, while pellets are drag-stabilized and prefer slow twists. Slugs need significant power to push them accurately and are mostly used in tuned PCPs producing 30 FPE and up. They are not a beginner's first ammo.