"ANY" gun should never be carried with the hammer resting on the firing pin or percussion cap if a ML'r. A hammer gun should have a safety notch, not generally a "Half Cock". Half cock is really a carry over from flintlock guns. The safety notch on a rebounding hammer gun is generally much more robust than the safety notch of a non-rebounder. Any outside hammer is vulnerable to being struck if the gun is dropped or you fall with it. The safety notch on many older guns is quite delicate & easily broken if the hammer receives a blow, in that aspect a hammerless is "Safer". in my well over 50 years of traipsing around while carrying a hammerless double I have taken two or three severe falls & yet have one to jar off. That's not to say they can't of course, its just not automatic that they will. Again the thing to prepare for is the "UnExpected". If nothing out of the ordinary ever occurred then only a complete fool would ever have a gun fire unintentionally.
Some of us with small hands & short thumbs cannot safely sweep back both hammers of an outside hammer gun. This is why I personally prefer using a hammerless & I never push the safety off till the gun is on its way to my shoulder. I don't push it off when doves enter the far side of the field or when I see the dogs go on point up ahead, only as the gun comes to shoulder. I have absolutely no problem with a gun having a single hammer but simply cannot handle two efficiently in a safe manner.
