Multiple (Colt, Smith & Wesson, Daniel Defense, etc.)

The AR‑15 is a lightweight, modular, gas‑operated rifle originally conceived as a military assault weapon and later adapted into a highly popular semi‑automatic sporting platform. Designed around a direct‑impingement gas system and a rotating bolt, its core philosophy emphasizes ease of maintenance, parts interchangeability, and ergonomic ergonomics that allow rapid reconfiguration with interchangeable barrels, handguards, and stocks. While the military‑grade M16/M4 family serves combat roles, the civilian AR‑15 is marketed for hunting, competition, and personal defense. Its distinguishing features include a flat‑top receiver with a Picatinny rail, a detachable box magazine, and a short‑stroke gas system that can be swapped for piston kits. The platform’s reputation is built on reliability, customizability, and a vast aftermarket, making it a benchmark for modern rifles and a frequent subject of legislative debate.