Every gun is loaded.
The “Every gun is loaded” assumption might not work well when heading into battle, with an empty gun … 
Sure, but where’s the gun pointed when you do that? Not at your face, hopefully! In any case, I doubt your instructions tell you to dry-fire the weapon. (Sorry, 40 ago I was very familiar with US issue Colt 45 automatics, but since then I’ve never owned or cleaned a handgun and I don’t recall the details.)
It’s a pretty damn rare occurrence, in my (ancient) experience, and that includes NRA classes with a bunch of 9-year-olds.
Bingo. Is it rare, as per my experience?
Ranges are set up to make it really easy to follow the rule. The targets are all downrange. Many weapons arrive in cases, and those that don’t are carried in using a fairly standard position. Weapons are placed on the range pointing downrange.
It’s a lot harder when hunting, especially with dogs (and most especially with someone’s poorly trained dog). There’s just a lot more variability. Still, it didn’t take long watching my grandfather and uncles to pick up the healthy practices, or get any unhealthy ones I was doing corrected promptly and calmly.
I only had to hear once the true story about my best friend’s father’s best friend leaning his shotgun against a fence as he climbed over it to never make that mistake. I confess I never understood how the gun could have gone off, but … well, the point is to assume it can at any time.
My uncle Dick has always been a real safety nut, following every rule to the letter. Being on the beach and using axes and chainsaws etc we got a lot of chances to see it in action, and we all used to joke a little about it a bit behind his back. One day I noticed he had a few black dots just under the skin on his legs and I asked him what they were. He told me that he and my Uncle Bob had 410’s and were chasing a squirrel around a tree and Bob’s gun went off. Well, that explained his safety-consciousness!
It should become such a habit, that it should actually take more effort to violate the rule than to follow it. It becomes instinctive, though you don’t rely on instinct to make it happen. When anyone breaks the rule, you notice it.
Glocks, for one.
Remove magazine, clear chamber, point gun in safe direction, pull trigger, continue to disassemble.
Hopefully, you have a back stop, ballistic bag/case or bucket of sand.
We have the bucket.
- Learn to love the Mozambique Drill.
To me, No. 2 is the obvious choice, as it is the premise that Nos. 1 & 3, the other two better choices, are based on. No. 4 is certainly good advice, but is not encompassing enough to be the most important rule of gun safety. Not that I didn’t enjoy No. 5.
What about a .308 Schrödinger? Until you look and the wave form collapses it could be either.
My number 1 is to remember to take and pass the firearms safety course before you handle a firearm.
Sure, but it’s not going to go off by itself and it’s not like I’m trying to shoot someone.
Both times I have touched a gun it was pulled out by a guy trying to impress me. I was still a teenager, and thought they were way cool. I assumed the guns were loaded but it didn’t occur to me that I needed to treat them in any kind of special way because, well, see above.
Obviously, I would be much more careful now.
Assume every gun is loaded and therefore you shouldn’t even touch it unless you’re fully prepared to kill/destroy or BE killed/destroyed (either by the over-reactive quick-draw vigilante over there or by the legal participants who will review your mistake in the aftermath).
Okay, yeah, this is a combination of the first three – kind of putting them all at #1
I figure once you’re fully prepared for such horrible consequences, perhaps you’ll treat it with the caution it requires.
–G!
Mister Saturday night
Special
Got a barrel that’s blue and cold
Ya ain’t goot for nothin’
‘cept puttin’ a man six feet in a hole
…–Ronny Van Zandt (Lynrd Skynrd)
…Saturday Night Special
…Nuthin’ Fancy
What you’re describing is, “Treat every gun as if it were loaded, regardless of its actual condition.”
This is very different from, “Every gun is loaded.”
I wholeheartedly agree with the first rule. The second rule is wrong, false, and should not be taught.
Not only that, but it’s the only round where we can’t determine the bullet’s momentum and position at a given instant in time. 
“Check the safety”
That’s the first thing that comes to mind for me. Make sure it’s on if you don’t want the gun to go off. Make sure it off if you need for the gun to spew bullets.
Nope. Safeties are a mechanical device. They can fail. Go with the three rules.
I didn’t say it was right. I said it was the first thing that came to mind. 
And back in the 70’s this was the received wisdom.
I guess you could play cuckoo with it.