The 38-70 was introduced in 1894. It was never a popular cartridge, not not really offering significant superior power over the 38-55, which also debuted in that year. 1886 rifles were available in 38-70 until it was discontinued around 1910. '86s in that caliber are somewhat scarce, yet don't seem to command a premium over rifles in the much more common calibers. I am not aware of any currently manufactured reloading dies or brass for the 38-70. If dies could be found, cases could be formed using 45-70 brass. keep your '86 as is, though. After all, they don't make 'em any more.
