The Pistol Caliber Carbine (PCC) actually penetrates more than a .223 with hollow point or soft point bullets.
The .223 bullets tend to break up quickly on hard surfaces, which limits over penetration.
Theres a reason why most LE agencies issue .223 rifles even for entry teams, it limits the risk.
From a pure survival standpoint, the 9mm carbine has a lot of positive aspects.
Low recoil so its easy for almost anyone to use, out of the longer barrel, the cartridge is more effective and still quieter than a pistol or larger carbine.
In some configurations it is extremely affordable.
The downsides? It doesn’t have the power of the larger, louder option.
It certainly doesn’t have the range. And it’s generally not legal to hunt larger game with.
For a while I have been telling people to pick up either a new pump shotgun (20/12ga) or an AR-15 as their primary home defense firearm.
In today’s world, one can pick up either for under $500 new.
Why not something “better”?
For most people, they aren’t going to go out and shoot thousands of rounds through either, so you don’t need chrome lining or heat shielding and the like. Firing a quick 30 rounds (rare at best), isn’t gonna destroy even the low end guns.
But I digress.
Testing the 9mm in gelatin and real materials, the 9mm generally penetrates 12-15″, even with the longer barrel.
I can say that the .223 using a 75gr match HP at 15′ will break the on side foreleg, penetrate through the lungs and finish breaking up going through the off side shoulder with no fragments exiting. And the fragments are quite small unlike the base of a 9mm bullet.
Light and fast .223 varmint load, 45-55gr bullets are pretty much the best for up close and personal work.
I’m not running around Afghanistan, so I can choose the most optimal load for my use and needs.
Your defense long gun needs a couple of things, a sling, a light and ammo.
Think about the range that we are looking at. I don’t need a $600 optic to hit a paper plate at 24′.
And if you can hit a 6″ paper plate every time across a room, that will end most hostilities.