The muskets (arquebuses) used by the Spanish conquistadors in the 16th century were even slower than that. They were lucky to fire 2 rounds per minute. But they also had crossbows, steel weapons, armor, and horses — as well as tactical doctrine which completely outclassed any of the primitive New World civilizations.

But disease did wipe out the majority of their adversaries, so they had a relatively easy time dealing with the survivors.