The boxlock action is a hammerless

Hammerless

A hammerless firearm is a firearm that lacks an exposed hammer or hammer spur.In rifles, using a firing-pin rather than a hammer is a substantial improvement because the time from trigger pull to firing can be less...

 action of a type commonly used in double barreled shotguns, dating back to 1875. The boxlock action was developed by Anson and Deeley, based on the earlier Westly-Richards action. The boxlock action uses concealed, self cocking hammers in a break-open action. Strongly opposed by most sportsmen and manufacturers at first, the boxlock action quickly become the dominant form of double barreled shotgun action.

Description

The boxlock action was the result of a long evolution of hammerless actions, created by two gunsmiths, Anson and Deeley, working for the Westly-Richards company in 1875. The contribution of Anson and Deeley was in the simple and elegant lock mechanism, which provided a hammerless action with fewer moving parts than exposed hammer models available at the time. This allowed a rugged and simple action which was faster to operate than exposed hammer guns. The original model, pictured above, used a hammer block safety, which was problematic, as it was possible for the gun to discharge when the safety was released. An 1882 improvement incorporated a trigger block safety, which was automatically engaged when the hammers were cocked. This type of automatic safety is still prevalent in modern boxlock actions.