What Biscuit Jake says is correct, as far as it goes. The .45/70 was adopted as the Army service rifle cartridge in 1873 for use in the Trapdoor Springfieldl,the same year as the Army adopted the .45 Colt in the Single Action Army revolver.

The .45/70 replaced the .50/70 as the governement's rifle cartridge. Alot of the troops said a .45 caliber was "too light for use against hostile Indians". Probably the same guys who earlier had complained that the .50 was too much of a reduction in caliber from the .58 used previously!

The original loadings used black powder, of course, and swaged lead bullets. The "infantry load" consisted of a 500-grain bullet and 70 grains of Fg or musket-grade black powder. MV of this load was around 1250 FPS from the long-barreled infantry rifle. The "Cavalry carbine" load used 55 grains of the same powder, and a 405-grain bullet at close to 1300 FPS.

Later on, when smokeless powders came along, smokeless equivalents of theservice rifle loads were developed, and for stronger rifles like the Model 1885 and 1886 Winchesters, a High Velocity load was marketed that fired a 405-grain bullet at around 1800 FPS. You can duplicate this load today with 53 grains of IMR 3031 powder and the jacketed 405 grain bullets made by Remington or Winchester. However, such loads should never be used in any rifles except newly-manufactured Winchester-Browning M1886's, Winchester single-shots, Ruger No. 1's,or other rifles of equal strength!

The .45/70 is extremely versatile in that one can load ammo for it from pure lead round balls at subsonic velocities for plinking use, all the way up to loads using very heavy bullets suitable for killing game like Cape Buffalo.

I have developed a load for my Ruger No. 1 that fires a 400-grain Barnes Original semispitzer (b.c. .389)at 2270 FPS (measured 10' from the muzzle) for an initial energy level of 4,600 ft/lb. This load groups into 1.25" for three shots at 100 yards, and shoots flatter than a .30/30 Win., so it is good on large game out to at least 250 yards, where it still delivers 2300 foot-pounds. I would not hesitate to use this load on the largest bear in North America.

In short, you can load a .45/70 to doanything you could do with a .30/'06, and then some!