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The first quantity manufacture of .45-70 at Frankford was in January 1874 and had a 405 grain bullet at 1350 fps, with a chamber pressure of about 19,000 psi. The case was inside primed (Benet) and made of a copper alloy commonly called "gilding metal". Over the years, many changes were made, mainly in case/primer construction. In 1882, a reloadable case with the Berdan primer was adopted, along with a 500 grain bullet. Four years later another reloadable cartridge, the Morse system, was adopted. Over the next years, there were several more experimental and test rounds made in more or less limited quantities. Even as late as 1897 tests were conducted with smokeless powder, a charge of 30.5 grains of DuPont No. 4 giving a velocity of 1428 fps with a chamber pressure of 18,000 psi with the 500 grain bullet. (Note that in this case, smokeless powder not only gave increased velocity, but did so at LESS chamber pressure, contrary to the usual belief that smokeless powder always means higher pressure.)
Carbine ammunition always used the 405 grain bullet, with a 55 grain (black) powder charge. As with the rifle cartridge, there were experiments, but not to the same extent. Adopted changes to the rifle cartridge case were automatically carried over to the carbine case.
FWIW, firing the 500 grain infantry load from a carbine is not a pleasant experience; the recoil is brutal.
Jim
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