The 1894 Winchesters chambered in .32/40 and .38/55 were also not marked for smokeless powder. Never heard of any issues there either. These rifles have been used with smokeless loads by hunters since the turn of the century with no ill effect.
The Winchester barrels were made of a different steel and Smokeless powders were already available in late 1894 when Winchester started making the 1894. The Marlin model 1893 was first developed in Aug. 1893 before Smokeless powder became popular. In 1895 they changed their barrels to a harder steel and started marking them Special Steel before changing the marking to Special Smokeless Steel. In 1905 they produced this B Grade Gun, as they called it, in a blued finished frame and
softer steel barrel. These guns were cheaper, $3.15 less then the standard Case Harden Frame, Smokeless steel barrel version. I have one of these B grade guns that has a small crack on the inside of the barrel which is not visable from the outside and I suspect that it was caused by someone using smokeless ammo in it.
I really think that most of the "For Black Powder" marked barrels were simply left over from the pre-smokeless powder era. Marlin was not one to waste anything, so to get rid of the older, soft steel barrels, they sold them as the "B" Grade, Model 1893's for less money than the Special Smokeless Steel guns. It was a win-win for Marlin and any customer that wanted to save some money.
If I had a black powder gun that I wanted to shoot, I would be looking to shoot low power, smokeless powder with
cast lead bullets. If I wanted to shoot jacketed ammuntion, get a newer gun made for jackteted ammuntion and higher pressures in a smokeless powder loads that will get the job done the way it should. So long as you use cast, lead bullets in a black powder gun, it will last as long as it was made to.
All I am saying is that is not recommended to shoot smokeless powder loaded cartridges in these models marked for BP only.
