When it comes to firearms, everyone has their favorite and “expert” opinion on why it is the best and better than your choice for the job of self defense. Again it extends to calibers and what they’re used in. I’m going to point out right now, no one round of ammunition will be perfect for every application or everyone’s need and ability. Just not going to happen.
First you have to decide on what kind of “Self Defense” you’re looking to address. What does that mean, you may ask? Self defense is self defense, right?
Self defense is the ability to defend yourself against a threat or attack by an assailant or assailants. One person, two people, several people? Is it someone trying to rob you, someone breaking into your home, carjacking your vehicle, home invasion by multiple threats, an attack by an animal, dog, bear, mountain lion? Mobile self defense, static self defense, daytime, nighttime? It’s enough to think about without just saying to hell with it, I’m going to use my cell phone and call 911 and let the police handle it. Well folks, the plain hard facts are, the police have no duty to respond to your emergency according to the US Supreme Court. It’s up to you to protect yourself and your loved ones.
The Best Calibers for Self Defense
You have to take in the factors of your age, physical ability and experience along with training. As you become older, folks are not able to handle recoil, or even pulling the slide back to charge their pistol or pulling the trigger of a revolver. So we’re going to talk about a few different calibers of rifle, shotgun and pistol for self defense.

Top: Weatherby .20 gauge shotgun Bottom: Weatherby .12 gauge Via Guns&Ammo

12 gauge bird shot shells are not the best choice for home defense Via SouthYorkshireAirguns
The 5.56×45/.223, 5.45×39, and 7.62×39 rifles and rounds are a choice for residential self defense made by many. One thing to remember is you are not bound by the rules of warfare when dealing with assailants. You can use frangible rounds, hollow points, soft points, loaded in a high capacity magazine as another good choice for self defense. I often hear people say, “My revolver with six shots is good enough against one person–if you don’t miss.” If revolvers with six shots were still the best choice, police would still be using them instead of hi capacity semi auto with spare magazines.

A Fingerprint safe for easy access in a home defense situation Via GunSafeCritics

Taurus 1911 .45 ACP that will pack a punch Via TheDailyCaller
Let’s talk about today’s world. I would say modern engineering of handgun rounds has leaped above what was available during the last several years so much it’s like comparing an old Model A to a new car today. Both take you where you need to go, but today’s bullets have breakthrough designs that now work like they’re supposed to. Similar to frangible ammunitions but better. Bullets like the Hornady Critical Defense and Critical Duty have a polymer tip that will expand the projectile almost 100% of the time.
Think of what happens when you press down on a rubber ball. It flattens out. This is what the polymer tip does to expand the hollow cavity of the bullet it is added to, whether it is .32, .380, 9mm or .45. The Critical Defense round is not a powerful as the Critical Duty round and is intended for the civilian market. The Critical Duty round passes the FBI penetration standards and is intended to reach though and hit an assailant who may be hiding behind a car door. The Hornady isn’t the only rounds out there now, and there are several companies who have engineered great leaps and bounds in pistol bullet designs for reliable expansion and transfer of enegry to the threat. It really is up to you do decide which will fit your need.

Sig Sauer P223 with a tactical flashlight for easy target acquisition Via GunBase

Its always better to have any gun than to not have one at all Via PixShark
There is not one round or firearm that addresses all issues of self defense. You should consider what the round is intended for, where you intend to use it and how you’re going to use it. While most folks laugh at the idea of a .25 auto as a defensive pistol round, so I would often point out, which would bother you more? Being punched or shot? Which would be more intimidating to the bad guy? Your fist or an obvious firearm?
In conclusion, regardless of what your caliber and firearm of choice may be, it is better than no choice at all. Just stick with modern, engineered and proven bullet designs. Lots of information out there about which ones work and which ones are gimmicks. Read up and learn, but most importantly stay safe and ready. For those of you interested in receiving a solid foundation of shooting skills and training, go to nrainstructors.org for availability in your area. I am located in Oro Valley, Arizona, should you like to attend training though our instruction: Murray’s Firearms and Ammunition.