Noun
boxlock (plural boxlocks)
(firearms) A style of double-barrelled shotgun with concealed, self-cocking hammers that use a break-open action.
A view of the break-action of a typical side-by-side double-barreled shotgun, with the Anson & Deeley boxlock action open and the extractor visible. Source: Internet
However, the most successful hammerless innovation of the 1870s was Anson and Deeley's boxlock patent of 1875. Source: Internet
The double-barreled shotgun has changed little since the development of the boxlock action in 1875. Source: Internet