Sheesh, of COURSE the US Army used smokeless powder in WWII. In fact, they used it in WWI. Anyway, this is supposed to be entertainment, not a history lesson. If you want Disney-style drama set in about the same time period, there are other programs you can watch. Little House on the Prairie comes to mind, for example.Oh, and @Vastly, actually, many people do fire smokeless powder from black powder pistols with a cartridge conversion. The stipulation is that the loads must be comparable to a black powder load, i.e lighter than those for a modern weapon.   See 3 other replies

Nice show.1) "Guns were prohibited in most towns in the West ": Actually- no. Some towns, notably the Kansas "trail towns", had laws prohibiting OUTSIDERS, I.E. the cowboys driving herds to the railheads, from carrying guns and those laws generally did not apply to local citizens. Some mining towns had local ordinances also, but generally, the "strict gun-control" of 19th century western towns is as much a myth as the daily showdown at high noon. But you are correct; most people did not carry sidearms on a daily basis. 2) Smokeless powder was commercially available in 1884, with both American and European companies producing it by 1890. I would not fire ammo using smokeless powder in a firearm designed to use black powder ammo. The resulting pressure would almost certainly destroy the firearm- and likely my hand.
But then again- it is a TV show, not a historical recreation.   See 3 other replies