Chassis
Also: Chassis System
A rigid metal stock system the action bolts into, offering modular ergonomics and a stable, repeatable shooting platform.
A chassis is a precision-machined metal frame, usually aluminum, that replaces a traditional stock by giving the barreled action a rigid V-block or bedding surface to clamp against. Because the action sits in metal rather than wood or molded polymer, the fit is consistent and does not shift with humidity or pressure, which removes much of the guesswork that hand bedding is meant to solve. The result is a platform that returns to the same point of impact shot after shot.
The other big draw of a chassis is its modularity. A chassis typically offers an adjustable forend with M-LOK or ARCA mounting, an interchangeable grip, a folding and adjustable buttstock, and detachable magazine support, all tuned without gunsmithing. That blend of repeatable rigidity and tool-free ergonomics has made the chassis the default home for serious precision rifle competition builds.