US Patent 8118203 Hammer-drive powder-actuated tool

A hammer-drive powder-actuated tool includes a hollow tool body extending along a front-to-rear direction, and a firing device disposed within a rear end portion of the tool body. The firing device includes a pin holder having a through hole extending along the front-to-rear direction, and a firing pin movable forwardly and rearwardly relative to the pin holder. The pin has a firing end portion that is disposed at a front end thereof and that extends into the through hole in the pin holder, and a central axis aligned with that of a rimfire cartridge along the front-to-rear direction. A front end of the firing end portion of the firing pin has a diameter larger than the inner diameter of the annular primer and smaller than the outer diameter of the annular primer.