Various barrel lengths and shapes (round, octagonal, half-round, etc.). Rifles chambered in "standard" factory rounds are warranted for shooting factory smokeless powder ammunition as well, such as the 30-40K, .38-55, and .45-70.
Rifles have different barrel lengths and shapes (cylindrical, octagonal, half-cylindrical, etc.). Firearms designed for standard factory cartridges can also fire smokeless powder ammunition, including rounds like the 30-40K, .38-55, and .45-70.