Warfare from the 1850s to the 1950s and the late adoption of high rate of fire rifles

I still maintain that practical machine guns were dependent on smokeless powder.

[EMAIL=“Poudre B - Wikipedia”]Poudre B - Wikipedia

http://en.wikipedia.org/wiki/Maxim_machine_gun

Another reason for the slow adoption would have been logistics. There’s no point in having a fast-firing rifle if the existing supply system can’t keep up with manufacturing and moving the additional amounts of ammunition required.

Broadly, I agree with you, but there were successful black powder cartridge based “Mechanical Guns” (ie the Gatling and the Nordenfelt) which were more or less the same thing as a machine gun, but operated manually (by a crank or similar contrivance) rather than simply holding a trigger.