The main problem with these rules is that they do not acknowledge that humans make mistakes (and guns can have mechanical failures) : a finger can slip and press the trigger, an external safety can be disconnected (and we think and act assuming it is still on), a thumb can slip while decocking a gun, the trigger might get pressed when holstering/unholstering, a round can be in the chamber even after we are "sure" the gun is empty, dry firing (and/or cleaning) a supposedly unloaded gun… racking the slide with the finger in the trigger… slam fire, mechanical failure in the decocking system, … etc, etc…
If you read carefully, you can notice that none of these potential 'deadly' scenarios are covered by the 'gun safety rules'
I disagree. The 4 rules cover all of these.
"a finger can slip and press the trigger" - except the gun is unloaded, and is pointed in a safe direction, so no one is harmed
"an external safety can be disconnected " - except the finger is off the trigger, the gun is unloaded, and pointed in a safe direction, so no one is harmed
"a thumb can slip while decocking a gun" - except the gun is pointed in a safe direction, so on one is harmed
These show how the rules overlap, but are legitemate concerns. They show why all safty rules must be followed
Now, the following examples are simply lists of people ignoring one of the 4 rules. No matter what list of rules you have, if your scenario entails people ignoring one or more of them, you have accidents. This is not a flaw of the rules, but of those who fail to follow the rules. Yes, if you break all 4 rules, people are liable to get hurt....but then, that's why we try not to break them.
"the trigger might get pressed when holstering/unholstering," - trigger cannot get pressed if the finger is not on it, so this is simply a violation, not an 'accident', besides, holstering should be done being aware of muzzle direction, so again, no harm
"a round can be in the chamber even after we are "sure" the gun is empty" -again, failure to follow rules (feel in chamber for round), also a loaded gun with a chambered round, no finger on trigger, gun pointed in safe direction. so again, no harm
"dry firing (and/or cleaning) a supposedly unloaded gun" - again purposely violating the rules, but good thing with muzzle control no one gets hurt, and when cleaning the finger is off the trigger, so no one gets hurt.
"racking the slide with the finger in the trigger" - again, voilating a rule, but good thing the gun is pointed in a safe direction, so again, no harm.
"slam fire," - violation of rules agian, but good thing gun is pointed in safe direction, so no harm.
"mechanical failure in the decocking system" - are we assuming violation of the loaded firearm rule? that's the only way this could cause a problem, but even then, good thing the gun is pointed in a safe direction. If anything this is an example of why ALL 4 rules must be followed. People get sloppy and think the decocker will work, but if it fails, the 4 rules will keep everyone safe.
Regarding your new list.
#1 - does not cover enough catagories. There are many times besides dryfiring when people are working with guns. 'NO DRYFIRING' doesn't protect someone moving a gun across a barbed wire fence, but the 'treat all guns like they are loaded' does. (meaning you are very aware which direction the muzzle is pointed, watch for any chance a wire can catch the trigger, even though you are sure the gun is unloaded, just incase you are wrong)
#3 - basically restates the standard rule with one extra irrelant clause thrown in for one specific type of firearm. What about single shot or double barreled guns, or revolvers? Plus this concept of not chambering a round messes with the rules of 'always consider a gun loaded' when you get into the catagory of 'half loaded' guns. The assumption that the chamber is empty is probably the biggest reason guns fire accidentally, but standard rule #1 covers them just fine. Your new rule #1 and #3 leaves a lot of situations where there are dangerous conditions not covered
#5 - why does it matter if gun is holstered or not, when the standard 4 on their own work just fine. Also, too many times when you have to unholster your gun, not just cleaning, target practice, or home defense. What about repair, inspection for damage, moving handgun from body to safe, moving handgun from body to case in car, examining handgun before purchase, etc etc. Also, this does not cover guns where no holster is available (like rifles and shotguns)
See, the standard 4 are really a beautiful set in how they cover ALL types of firearms in ALL conditions. Your attempt to build a set around just handguns and just certain circumstances leaves too much unconsidered, and allows for dangerous situations your rules are simply silent on.