The six-shooter made the individual more powerful than ever before. The pistol, being carried on the hip, was more portable than the rifle while leaving the arms and hands free. That meant that the weapon could be carried as a permanent part of the individual's wardrobe without regard as to location or task. Quickly accessible, the individual could get six quick shots off with enough caliber and range to inflict significant if not fatal damage.
This is why the colt revolver was so significant in the history of the old west.
Here's an article from Popular Mechanics by Matthew Moss: http://dld.bz/feS9p
Frederick Jackson Turner's book on the Frontier in American History in The Basic History Library (free). ------------->