.45-70 Government (using Sierra bullets)
Date: May 23 2019
As it implies, the .45-70 Government started life as a military round in the U.S. Model 1873 Springfield rifle which, due to its rather unique breech mechanism, is better known as the “Trapdoor.” The cartridge quickly became popular among civilians in a variety of single-shot rifles, and especially lever-actions rifles, such as Marlin Model 1895 and Winchester Model 1886. It was originally a Black-Powder round, but as smokeless powders appeared, factories made the switch and offered both types of ammunition for many years. Only the smokeless loads are currently offered by major ammunition companies. Current industry pressure guidelines are established at 28,000 CUP; however, factory load pressures are notably less than this figure. Federal Cartridge, Remington and Winchester advertise a 300-grain jacketed bullet at velocities between 1,810 to 1,880 fps, while Remington still offers the proven 405-grain JSP bullet at 1,330 fps.
The accompanying data was developed specifically for modern Marlin Model 1895 Lever-action rifles produced since 1972.
Most of the accompanying data developed with 300-grain Sierra JHP and JFN bullets utilizes less than 100 percent of the case capacity. This leaves air space between the base of the bullet and the powder, and as a result there is no powder “support” to the base of the bullet. This makes it essential to apply a heavy roll crimp to prevent bullets from becoming deep seated when placed in a tubular magazine, where they are subjected to spring pressure and recoil.