Abstract: A muzzle loading firearm, such as a rifle, having a firing nipple which communicates with the rear of the barrel bore and mounts thereon a firing cap. The nipple is positioned within a chamber formed in the interior of the stock directly adjacent the rear end of the barrel. The chamber opens outwardly through one side surface of the stock. An openable and closable cover is mounted on the stock adjacent the side surface thereof for permitting closing of the chamber. The trigger mechanism is mounted on the stock substantially forwardly from the firing nipple. An elongated firing rod is slidably mounted internally of the stock and projects forwardly from the chamber to the trigger mechanism. A latching structure coacts between the trigger member and the firing rod to hold same in a forward position such that, when the trigger is activated, the firing rod is released and spring urged rearwardly to impact against and detonate the firing cap.