cap or tube primers respectively. Scent-bottle lock refers to a design by Forsyth. The charger containing the fulminating powder resembles a scent bottle in shape. Breechloaders Early breech-loading, cap lock longarms, such as the Sharps carbine and the Wilson carbine used much the same side mounted lock mechanism as muzzle-loading cap-locks. Revolvers The commercially practical revolver followed from the advent of the percussion cap. The action of cocking the hammer is used to rotate the cylinder and bring a loaded chamber in-line with the barrel preparatory to firing. The mechanism for cocking, rotating and firing revolvers is contained between side-plates that form the frame of the revolver. This is a significant departure from earlier lock mechanisms that were constructed about a single plate fixed to one side of a firearm. Metallic cartridges Metallic cartridges package projectile, propellant and primer together. They are initiated by striking with a firing pin or striker that passes through the breechblock. Early metallic-cartridge, single-shot breechloading rifles, such as the Snider–Enfield and the Springfield model 1873, continued to use side-mounted hammers and lock mechanisms that differed little from the cap lock and the flintlock in manufacture. The firing pin is angled away from the axis of the barrel and toward the hammer, to accommodate the offset of the hammer. The further development of breech-loading mechanisms and repeating firearms placed the components of the mechanism within the receiver or frame of the firearm. This can be seen in the Martini–Henry, the Remington-Lee Model 1879 and the Winchester rifles. The mechanism employed to open and close the breech is integrated with the firing mechanism to cock the firearm. Improvements in spring technology has also resulted in cheaper helical coil springs in place of leaf and V springs. The term lock is not generally used to refer to the firing or trigger mechanism of metallic cartridge firearms. Boxlock Side-by-side shotguns and hunting rifles continued to use side-locks until the advent of the boxlock patented by Anson and Deeley in 1875. Side-lock shotguns have two separate lock plates mounted to the sides of the butt of the gun and not the receiver. In the boxlock, the components of the firing mechanism are contained within the frame of the gun. This simplified manufacture and significantly reduced costs. While the boxlock is referred to as a hammerless gun, the hammers of the mechanism are concealed within the gun's frame. Side-lock shotguns continue