There was a time when the aphorism “Six for sure,” carried significant weight and automatic handguns were not nearly as dependable as revolvers. That time is long past, though. Modern automatic pistols are extremely reliable when loaded with quality ammunition.While revolvers are certainly no less dependable than they have always been, they are no more perfect than any other thing made by man. No matter what that gentleman with the greasy John Deere hat who seems Krazy glued to the end of the gun counter told you, revolvers can malfunction.
Aside from problems than can plague any firearm like parts breaking or bad ammo, there are problems that are unique to revolvers. A bullet can jump forward due to inertia when fired, locking up the cylinder. Debris can get between the hammer and the frame or between the frame and the cylinder. The latter can prevent primer ignition, stop the cylinder rotating, or prevent it indexing properly and the former can prevent the firing pin making contact with the primer or the hammer making contact with the firing pin. All that is not meant to imply that the revolver is in any way less reliable than an automatic, but it does have limitations.
by Andrew Betts