Parameters affecting risk of accidental discharge of a dropped handgun:
(1) type of gun
(2) expense used to produce (cheap and poorly made vs well-made and tested)
(3) safety features
(4) deterioration (rust, etc.)
(5) impact (height dropped, surface struck, etc.)
Types of handguns:
(1) single action revolver
(2) double action revolver
(3) derringer
(4) strike-operated automatic
(5) external hammer automatic
(6) internal hammer automatic
The handguns with highest risk of accidental discharge are single action revolvers and derringers. An automatic with an internal hammer has the lowest risk.
General risk factors for accidental discharge:
(1) absence of a safety mechanism
(2) poorly made
(3) deterioration or tampering
(4) high impact
Risk of firing a live round in the chamber:
(1) a single action revolver:
(2) derringer
Steps to prevent accidental discharge of a handgun:
(1) Use a handgun that is designed to be safe (with a hammer block, safety lever, etc).
(2) Do not modify the gun.
(3) Keep the gun clean and properly working.
(4) Avoid dropping the gun.
(5) Do not chamber a round until it is needed.