I can also remember . . . and I think it was in the original "Alamo" done back in the early 60s . . . . where some 45/70s were altered to appear to look like flintlocks. I guess you'd have to say that some of the more recently done movies have at least been an effort to keep authenticity.
I always found it a little disappointing to see some historical movies . . . which could/should have been excellent . . spoiled by the use of incorrect weapons and accouterments. I guess a lot of folks wouldn't know the difference but for someone who is a history buff, it can sure spoil the effect in a hurry. Things like a Civil War movie where the actors are dressed in 5 button sack coats with McKeever cartridge boxes - 45/70 rifles, etc.
Or, a good western that takes place in the 1870s and the actors are armed with Winchester 94s.