Abstract: Rifling for the barrel of a firearm includes a first gain twist region for increasing the rotational velocity of a bullet as it travels from the breech towards the muzzle end of the barrel, and a second region in which the rifling is of a constant twist so that the bullet exits the muzzle end of the barrel at a constant rotational velocity. The bore defined in the barrel is tapered in a direction from the breech end to the muzzle end so that the diameter of the muzzle opening of the barrel is less than the diameter of the breech opening. The angle of the rifling is variable with the rate of the gain twist of the rifling. The gain twist of the rifling in the barrel is formed by a button, preferably having a sinusoidal shaped periphery, which is pulled through the barrel during the manufacturing process. The smooth periphery of the button prevents shredding of the barrel when the button is twisted at different speeds to provide the variable gain twist of the rifling in different sections of the barrel.

Abstract: Rifling for the barrel of a firearm includes a first gain twist region for increasing the rotational velocity of a bullet as it travels from the breech towards the muzzle end of the barrel, and a second region in which the rifling is of a constant twist so that the bullet exits the muzzle end of the barrel at a constant rotational velocity. The bore defined in the barrel is tapered in a direction from the breech end to the muzzle end so that the diameter of the muzzle opening of the barrel is less than the diameter of the breech opening. The angle of the rifling is variable with the rate of the gain twist of the rifling. The gain twist of the rifling in the barrel is formed by a button, preferably having a sinusoidal shaped periphery, which is pulled through the barrel during the manufacturing process. The smooth periphery of the button prevents shredding of the barrel when the button is twisted at different speeds to provide the variable gain twist of the rifling in different sections of the barrel.

Abstract: A single "L"-shaped modular building unit comprises an integral end wall and ceiling and incorporates an outwardly depending flange peripherally surrounding the entire modular unit. The overall ceiling length is equal to twice the ceiling width. The outwardly depending peripherally surrounding flange is rectangular along its exposed edge to provide a modular unit which can be easily interconnected with similar units in any desired arrangement. Along the interior facing edge of the flange, the overall rectangular shape incorporates radii of curvature at the ceiling-wall interface for additional aesthetic purposes. The interconnecting portion between the wall and the ceiling is a saddle-shaped curve extending both longitudinally and laterally substantially the entire length of the ceiling and down a substantial portion of the wall.