Rolling block

The breechblock is locked into place by the hammer, therefore preventing the cartridge from moving backward at the moment of firing.

[clarification needed] It is a strong, simple, and very reliable action, that is not prone to be jammed by debris or with rough handling.

[4] The first firearm based on it, the Model 1865 Remington Pistol, was offered for sale to the United States Army and Navy in 1866.

[7] Remington built estimated 1.5 million firearms with rolling-block action, encompassing rifles, carbines, shotguns and pistols.

[8] A single-shot action developed by Barton Jenks from Bridesburg, Philadelphia right after the Civil War was locked not by the hammer itself, but by a separate hinging piece on the breechblock; it was tested by the US military in 1866 but not adopted.