Interesting thread. I note a lot of posts from some who know little about the M1 carbine.
The sheriff’s department I work for bought 60 surplus USGI M1 carbines in 2001. I had the privilege to overhaul these rifles and make sure they were in 100% operating condition so as to issue to sheriff’s deputies for patrol rifles/carbines.
The story behind these M1 carbines and the process of reworking them is interesting in itself, but the point I want to make is that we did extensive testing with the M1 carbine and the .30 carbine round before we issued them to for patrol. I'm not going to debate whether a AR or AK or even Mini-14 is "better" than a .30 carbine, but I can say that the M1 carbine can more than hold it's own as a very effective, modern use, patrol firearm.
My first hand test showed that the .30 carbine does defeat standard auto body and auto glass. It also defeats Level II body armor. With 110 grain Winchester soft/hollow points it is a very effective one shot stopper and I've taken a number of white tail deer with this round (I'm not recommending it as a deer rifle, but it can do the job at appropriate ranges). I've also had to down a charging bovin, two rounds and it was down.
After tuning these carbines with new springs and replacing worn parts as necessary, I was involved with sighting these rifles in and they can be very accurate. I found parts and magazines to be readily available.
For those who say the .30 carbine does not have the terminal ballistics to do the job, I can confirm it's not a main battlefield rifle by design. But it is certainly not whimpy, and if you ever shoot it next to a pistol caliber carbine in 9mm, .40 S&W, or .45 ACP, you will see that it is significantly more powerful. Significantly more. I am duty qualified with a number of firearms which include both a M1 carbine and a Ruger PC4 in .40 S&W, and though I really like the PC4, the M1 carbine is more accurate and produces less felt recoil. After shooting quarter inch steel targets and 100 yards and there is no doubt that the .30 carbine is the more powerful round by a wide margin.
In summary, I would heartily recommend a M1 carbine as a home defense or even as an effective LE patrol carbine. I'm not going to debate it's merits as compaired to black rifles, AK's, or even the .30 carbine vs .223. There are pro's and con's both ways. I've carried a M1 carbine in M1A1 configuration as a patrol rifle for 9 years and I have never felt undergunned with it. I have shot mine competively in LE compititions and have been able to hold my own. I'm not saying it's the best LE carbine out there, but for those who say only a .223 type will do, I would have to disagree.