The following information on single action vs double action shooting comes from Section 58 of Shooting by J. Henry FitzGerald. Shooting is also available to purchase in print.
A revolver may easily be rendered useless by striking some one over the head with it, if the blow is not properly executed. If a four, five, or six inch barrel is used and the muzzle should strike the object first it would be very liable to bend the best revolver barrel ever made. Also if the right side of cylinder should strike the object first it might spring the crane and force the cylinder out of line with the barrel. This might happen to any revolver whether locked at the front end of ejector rod or not.
The proper way to use a revolver as a club is to strike from the right, bringing the left side of cylinder against the head or other part of the anatomy; a needle and thread will repair all damage.