This is a question we hear on an almost daily basis and my standard answer is that depends, what are you going to use it for.
From a purely defensive mindset I can think of three or four separate purposes and surprisingly enough your skill level is self-defense has a lot to do with which gun works best for each individual purpose. The answer we hear most is home defense. Unlike many people we DO NOT recommend a small, untrained woman by a Remington 870 in 12 gauge because we do not subscribe to various wild theories 1) that you don’t have to aim it, 2) that the sound of the slide racking will frighten everyone away, 3) that it won’t hit your neighbors house, or 4) that it is the most devastating wound (please note you have to hit what you are shooting at to have a devastating wound). If you don’t regularly practice with a gun, it is not the gun to use in a violent encounter, so first is, the gun must be fun to shoot.
In home defense our standard recommendation for a beginning shooter is a full size semi-automatic from a manufacturer with a known history of zero failures, in a caliber with a proven history of stopping bad guys. We will save the obvious questions on that statement for another blog. We also assume the shooter is a student or will be so their ability to handle correctly is assumed.
the best gun for home defense would be a semi-automatic carbine loaded with .223/5.56 ballistic tip ammunition. Now I can already hear the howling of the “experts” who do not teach for a living but the fact is there, a 5.56 has the best rate of fire, has the best wound cavity, can be shot very fast and accurately and . . . DOES NOT OVER PENETRATE, thus the purpose of the blog.
The wound cavity of this round makes about a 3” to 4” diameter pile of hamburger shortly after entering the body and generally if anything leaves the body it has no mass and is therefore much less lethal. If your predator requires physiological damage to cease the threat, this is a good way to do it.
Considering the high velocity of this round when it penetrates drywall the bullet essentially comes apart as compared to ALL others thus greatly reducing the risk of someone in the next room receiving a lethal injury.