chamber to chamber. The chambers must also align consistently with the barrel, so the bullet enters the barrel the same way from each chamber. The throat in a revolver is part of the cylinder, and like any other chamber, the throat should be sized so that it is concentric to the chamber and very slightly over the bullet diameter. At the end of the throat, however, things change. First, the throat in a revolver is at least as long as the maximum overall length of the cartridge, otherwise the cylinder cannot revolve. The next step is the cylinder gap, the space between the cylinder and barrel. This must be wide enough to allow free rotation of the cylinder even when it becomes fouled with powder residue, but not so large that excessive gas is released. The next step is the forcing cone. The forcing cone is where the bullet is guided from the cylinder into the bore of the barrel. It should be concentric with the bore, and deep enough to force the bullet into the bore without significant deformation. Unlike rifles, where the threaded portion of the barrel is in the chamber, revolver barrels threads surround the breech end of the bore, and it is possible that the bore will be compressed when the barrel is screwed into the frame. Cutting a longer forcing cone can relieve this "choke" point, as can lapping of the barrel after it is fitted to the frame. See also External ballistics Percussion cap, for an early history of priming powder and percussion caps Terminal ballistics Transitional ballistics Physics of firearms Table of handgun and rifle cartridges References External links A (Very) Short Course in Internal Ballistics, Fr. Frog QuickLOAD Ballistics Software Ballistics Ammunition Handloading