Carbines are wonderful pieces of history. I have several and have shot and enjoyed them for many years. Young men also need to learn some of their history. For possible serious issues keep the Ar15 for yourself. No question.
First line of defense are my 9mm pistols that stay loaded with 147g HST defense ammo. If things escalate, my Advisor Carbine with laser is ready, also loaded with defense ammo.
Before even getting to cartridge and ammo selection discussion I am going to take the AR15.
You can do almost everything from 10 to 300 meters (maybe a bit further) with a single properly equipped AR15 and a couple different mags of ammo. Carbine just doesn't offer that flexibility which is why I would go AR. You don't need to have the rifle filled with tacti-crap, just a flash light and optic of choice will get you through a lot.
The M1 Carbine is more analogue to modern PDWs, the FN PS90 comes to mind. A compact easy handling gun to replace a pistol that will get the people with it (truck driver is always the stereotype example) out of trouble. 5.7 offers the flexibility of AP options too but the ammo is very hard to get in the US and performance in the full length barrels is so so, plus the terminal ballistics of normal ball aren't impressive to me. However, the AR15, especially with optics, will out range both. Since this scenario said home defense AND SHTF scenarios that is why I say AR15
There is a lot that can be written about bullets, penetration, cartridge, etc. I will say that in the event of a miss, it doesn't matter really what you miss with - .223, .30 carbine, 9mm, 00, it has the potential to go through a lot of drywall until it hits something and numerous tests have shown this. But the rifle itself just doesn't stack up for me. And I love the Carbine, I just think it's time has moved on and it is now firmly a fascinating collectible versus a duty gun.
Self defense is going to be a little hard to justify at ranges beyond a few yards, unless the BG is shooting at you first. There may be no need to be considering a SD round for anything past 100-yards. Shotguns and pistol-caliber weapons seem very appropriate for that and I won't fear shooting my neighbors up in the process. I think the M1 carbine is a good choice. I have a 9MM AR and a 9MM M1 as well and they seem "more perfect" for the role to me and are very economical to shoot in practice as well. If I want to reach out and touch something, I have a 5.56 for that purpose.
I wanted one of these because this is how I envision my sons and I dealing with a nocturnal threat, but the guy at the guy shop just stared at me. Apparently he hadn't a clue where to order the backpack part of the rig from.
If you ever shoot a centerfire rifle, carbine or shotgun inside a house, without ear protection, you'll never forget it. I'm with Jim on the penetration issue too. This is why I actually sold my shotgun and replaced it with a .40 cal pistol-caliber-carbine (PCC). Along with handguns, this forms the basis of my HD array. I live in a typical subdivision with homes on all sides. I still have ARs and an AK but they are more for area defense should that ever be needed. This scenario is actually getting more possible if the 'protests' and groups like 'antifa' take it up just one more notch, to come into residential areas to 'punish' the 'pigs' who 'unfairly' enjoy a half-decent lifestyle after decades of hard work instead of 'sharing' it with socialists.
'Really Senior Member' Especially since I started on the original Culver forum. That had to be about 1998.