_Rifle._—A gun having grooves cut parallel with each other along the interior of the barrel. They usually take a more or less spiral course for the purpose of imparting to the bullet thrown a whirling or twisting motion on its flight through the air. The grooves thus cut are sometimes called rifles. _Rifle._—A gun with grooves cut in a twisted or spiral-like manner on the interior of the barrel, for the purpose of giving the projectile a rotary motion on its axis during its flight. The design being to give greater accuracy to the course of the bullet. _Rifle Cane._—A metallic walking staff, which is virtually a rifle, capable of shooting with much force. The lock works internally, and everything is so arranged as to pretty effectually conceal the true character of the arm, it, at a casual glance, presenting only the appearance of a neat walking-stick. _Rifle Guide._—An implement used by the gunsmith to guide the course of his rifle-saws in cutting grooves in the bore of a barrel. _Rifle-Saws._—Short files made to fit in the grooves of a rifle. They are usually attached to a rod, near the end, and drawn to and fro through the gun for the purpose of filing the grooves down to greater depth, where such a thing is required. In cases where new grooves are to be cut in a smooth-bore, the rod passes through a rifle-guide, which forces the saws to take the proper twist through the barrel. _Rim-Fire._—A cartridge whose ignition is around the rim instead of in the centre, and which, consequently, can be used only by some arm striking the cartridge at the rim. _Rouge._—A fine powdery material, used for putting a high polish upon the surface of well-finished metals. It is usually applied by rubbing in connection with soft leather, either in the form of a buff or otherwise. _Saturated Solution._—A liquid holding in solution as much of some particular soluble chemical as it will dissolve. For instance, if salt be put in water until a portion remains undissolved at the bottom of the vessel, there is in the liquid a saturated solution because it holds in suspension all the salt that it can dissolve. _Scatter._—When a shot gun throws the pellets over a range of space unusually wide, it is said that it scatters. _Scroll Guard._—An extension downward from the trigger guard, to steady the hand. It is designed to answer the same as pistol grip. _Sear._—Sometimes called dog, which see. _Sear-Spring._—The small spring in a gun-lock which presses the sear into the notches of the tumbler. _Set-Triggers._—See double-triggers. _Side-Lever._—A lever which works at the side of a breech-loader. _Side-Screw._—The long screw holding the lock to the stock. _Slack-Tub._—A vessel containing cold water, to be used in suddenly cooling hot metals, as in hardening steel, for instance. _Smooth Bore._—A gun for throwing single bullets, made on the plan of a rifle, but having no grooves in the bore. It is sometimes called a “smooth-bore rifle.”