The Browning incident mentioned above most likely involved an early model that did not have the second safety notch on the hammers.
Re safeties and sears. I have taken enough guns apart to see that the safety in the vast majority blocks the trigger, not the hammers. A gun can fire with the safety on. As noted above it can fire if the intercepting sears are not regulated properly, and more importantly if they are clogged with dry oil and grease.
On the other hand an OPEN action just cannot fire. There is no reason to close a gun till an active hunt phase starts, ie the dog goes on point, the birds fly over in pass shooting. This business of walking witha closed action while not in an active phase just does not make hunting sense.
An added plus, you cannot foget to close a gun the way you forget to disengage the auto safety.
