When a round is chambered in a trap gun, it is cocked and ready to rock. That’s the nature of trapshooting.
Not that I’d trust any safety and I treat every gun as loaded, but a manual safety on a shotgun indoors would sure be a lot gentler on the sheet rock.  
And then the gun is “broke” as I said, ist in “safe”mode.
Remington 32 skeet, have an “on/off” safety, and a separate trigger selector,
Don’t bring a knife to a gunfight
Makes an already long gun even longer and less maneuverable, virtually all uses of a shotgun in home defense are going to be handled without a bayonet, and for those uses the bayonet is a hindrance more than an asset
Even military and law enforcement virtually never use or have a use for bayonets, it’s just not a practical thing.
Your physical speed and strength are a factor in using something like this and I suspect most defenders are physically inferior to violent criminals invading homes…and the majority of the length of the gun is a great surface to grab hold of and gain control.
Really though, I kind of feel like the answer is “because this isn’t Hollywood and I’m not Jason Bourne”
I can’t really argue with the basic logic, an affixed bayonet is a spear or tip slashing sword at best.
And yeah, I’m 47, dad bod out of shape… but I know how to handle swords, spears, and guns… the average idiot home invader is likely to be much younger than me,… probably even stronger than I….
However, the average home invader probably isn’t expecting to be shot at then have to defend against a spear that may explode and remove their arm if it’s still loaded…
Just saying.
Grabbing the business end of a shotgun in my mind and the scenario by Will_B would be a poor choice bayonet or no bayonet.
Ok, but what type of ammo should we use? If it’s a semi auto shot gun. what combo of ammo should we load into it, and in what order?
Bird, buck, slug. I had no idea what chokes were until I studied them, and I wonder - if we are gonna load a variety, then should the choke be a “cylinder” type choke?; For our own safety and safety of the gun - so not to damage it?
It’s easy to forget - the first you load is the last that shoots out. The last you load, is the first which is fired.
Once heard a theory - the first shot should be “bird”, second being “buck”, third and all subsequent being all “slugs”? ; for frightening, bird then buck for slightly less lethal, ethical reasons, but of course that’s always a discussion, debatable and subject to one’s personal preference. Buck of course, also known to be fatal.
Considering thin walls, if you have family in your home, friendly fire, etc.
Not that SD would be at a distance, but I realized my barrel was smooth, so I recently purchased some rifled slugs for accuracy.
Things to consider. Interesting. Been planning to check out an outdoor range I’ve yet to try, ought be fun, no pun intended. Especially since it’s near a fishing and hunting hole.
Pick one. I keep it loaded with OO Buck with several Slugs in a sidesaddle if needed.
The only birdshot I use is Steel T-shot (i.e. Poorman’s Fléchette).
5 rounds of 00 Buck. Probably 4 rounds too many but keeps BERTHA well balanced. 
Save the gonna kill the neighbors crap please.
Sooooo,… the 14 rounds of 00 in my DP-12 might be considered excessive?
Not if you’re expecting the zombie apocalypse. If so buy more DP-12s or more ammo for the 50.
I myself would prefer the 50 to keep them at distance…
Well, I only have 255 rounds for the .50 left…. That thing is expensive to feed!
Have all 500 rounds of 00 for my DP-12,….
And I’m pretty sure if I used my .50 in home defense, I’d get the perp, the perp behind him, the getaway accomplice in the car in the street, and their other buddy robbing the house a block away….
That wouldn’t look good in court, just saying
….and clip Noosehim’s ear.
Is hair gel flammable?
Asking for a friend.
I’m not THAT good of shot!
Buckshot, Buckshot, Buckshot, Buckshot, Buckshot, Buckshot
For mine. That’s a 6 shot tube, I keep ready shotguns set by putting 6 bucks in the tube, then releasing the last one onto the carrier. Action closed. Safety on. So have to chamber a round and then all that’s left is the safety.
(as a general rule, shotguns are not drop safe)
Yep, you need to have 7 slugs in one tube and 7 00 in the other. Choices matter! 
That’s not much of a choice though with the way the gun works…
It would be buckshot, slug, repeat.
If anything I might load 3 slugs into both tubes first, that way I have 8 scatter shots to wing them with and 6 slugs to finish them off?
I’m not sure how the DP-12 loads. In my Keltec I can switch between tubes on every shot. Probably not real useful in a home defense situation but I still like choices just in case.
Hey, I didn’t ask that one! 
It’s a side by side, each wrack chambers both barrels, the trigger is sequential, so wrack it once pull the trigger twice.
What do you all think about the use of the shorter shot gun ammunition, such s 1.75" Mini Shells?
I read it can allow for adding more capacity, less recoil. Could it have advantages for in home SD?
Would the range/distance be diminished? How can you tell if the shot gun is full?; Would you “see” or feel the resistance? Would it being too short to fit safely in all shotguns? Any concerns of feeding properly through semi automatics?