Actually, there are at least 3, when you include hardware failure, either through misdesign (very rare), or simple failure. I know someone who had a disconnector failure on a 1911. It caused the weapon to discharge all 9 rounds in one trigger pull.
Mark
Now here's a case of a real AD, if the owner didn't cause it by his own inept "smithing". That would move this into the ND category, the way I look at this.
See the replied-to post.
If the safety rules are being followed, mechanical failures should not result in injury or property damage.
1. Always keep the muzzle pointed in a safe direction.
2. Always keep your finger off the trigger until ready to fire (sights on target).
3. Always keep the firearm unloaded until ready to use.
Obviously, one or more of these rules was not adhered to.
Sweet! How do you make that happen?