In the grand scheme of things considering all possibilities no matter how remote, the only acceptable self defense firearm is a .50 Barrett with alternating armor piercing and incendiary ammo coupled with a call into air support to a drop a moab on a remote hillside. Because why not
since I can't find the obvious joke font, I'm pointing out specifically the above is supposed to be humor and not me trying to be a jerk
But if we're going to group every possible scenario where you may have to defend yourself together as self defense, the 50 has to be included.
Here is my rationale.
I limit "true sd" as out to 7 yards for a couple reasons. The first is just simple logic. Nobody is going to step into the alley 50 yards behind you and announce that they are coming to rob/murder/rape you (hopefully in that order). The Bg will always close distance with you. They want to grab you they want to be able to conduct their business at no louder than a normal speaking volume. Typically if things go right for the bg they will close enough to boop your nose before you know they're a threat.
If you can gain 50 yards of space, odds are you're safe. No reason to stop and fight, keep going. Your goal is to escape, not to fight. My job was (thankfully not anymore) to be the guy who went into the alley to fight. You get safe, let me work.
Which brings me back to my sights being pointless remark. You'll be able to press the muzzle into their ribs, if you miss then, no sight is going to help.
2nd, 7 yards puts the bg well into threat range. An average man can cover 7 yards and stab you in the neck in less time than it takes A WELL TRAINED and most importantly PREPARED cop to draw from a level 1 holster and place 1 shot on target. The only thing faster than a lvl 1, is already having the pistol in your hand. Cc holster are slow and clumsy in general.
Also 7 yards is about the limit an average person can point aim and place a round on target. When I was much more practiced I could do it consistently to 25, but I carried an expert rating and put a metric ton of lead downrange every month.
So your target is both within viable threat range, and in viable target range at the same time. At 50 yards, they are a possible threat, and a possible target, assuming both you and they are well practiced with a pistol and capable of putting shots on target at those ranges. If you are not a 50 yard shot with a pistol (few are) *while being shot at yourself and scared out of your mind* (which almost nobody is), it doesn't matter what you're carrying. A starter pistol with blanks will have the exact same effect as a 9mm, a 40, a 45acp etc.
Ask yourself, realistically, *How food am I at 50 yards? How good am I at 50 yards while I'm jumping up and down, ducking, juking, probably peeing myself, crying, while my target is doing the exact same thing?* How much ammo do you carry? My duty carry was 14 in the gun, 2 mags of 13 each. That gave me 38 attempts to make 1 count, and we definitely trained to not spray and pray because 38 goes a whole lot faster than you think when you really don't want to die.
My sd if I'm carrying a pocket, 7. 6 more with a spare mag. Can I honestly afford to waste ANY of those 12 rounds just making noise, which I am statistically likely to do at an extended range?
It will either evoke an "oh [beeep] they're shooting at me" reaponse, or it won't. If it does, success. If it doesnt, you're dealing with a severe problem and escape is really at the top of the list of things you really want to do.
But we're getting away from sd, mainly because that's not the way sd generally works.
My past career, 50 yards was a real possibility. 200 yards, real possibility. I carried different tools, because I'm not worried about sd, I'm hunting. In that case, I need effective tools at extended ranges.
If I got surprised at 50 yards I have a few options depending on the situation.
1. Middle case scenario, I can take cover and apply pressure while others take a superior position. That either forces bg to stop fighting or my help stops the fight for him.
2. Best case scenario. My car is nearby and I use my pistol to fight my way to the trunk. The car provides me cover, which is good. And ask anyone that worked with me what to do in a firefight, and they should answer "get to my trunk". ALL THINGS GOOD lie in my trunk
that includes ammo for every caliber you might be carrying from 9 to 45 along with .223 and 12ga in 00, slug, beanbag, spare loaded glock mags for ease of use and the thing I really wanting to reach in that scenario, my rifle and my mag pouch with 4 fullY loaded 30 round mags. That gives me 150 rounds of .223 and [beeep] is about to get real. Some officers chose to carry spare blankets, and a whole lot of empty space in the trunk. I chose to get crappy mpg, I didn't have to pay for gas (or the ammo) so I didn't care.
Tldr, your pistol is what you use to fight your way to your long gun.
Or 3. The suckiest option, I close with you and I'm making noise the entire way. But I want to keep pressure on you until I'm scoring hits.
But tangent aside, I'll stick to my recommendations