Me too though JB brings up a good point. They would make a good option for certain limited situations.
I talked to a Korean war vet about a month ago and he had one for about 3 days. After he was rushed by an enemy trying to bayonet him "I gave him 15 rounds as he was coming at me, ran dry, deflected his charge, and that Chinaman just kept on going! Probably deep into China, I never did find him". He was able to turn it in and got a Garand very shortly after that. Probably be a bit better with HP or SP ammo, but I wouldn't want one, not with ball. Why is it they are so expensive?
I've never been in combat, shot a gun at anyone (dead or alive), and doubt that 'my opinion' should even be considered in the same stratification as a combat vet.
However, this story seeths of bunk. The stories about the vain 'stopping power' of the 30 Carbine never seemed to be common until after Korea, when hypervelocity 223 ballistics became 'en vogue'. I'm sure you've heard them too... tales about a squad of GI carbiners emptying mag after mag into a N. Korean, capturing him unscathed after a footchase, and witnessing a bunch of 30 slugs falling out when then when they unfurl his frozen, but perforated, bedroll.
Time after time, the skeptics eventually are proven the 110gr ball slug has plenty of energy at effective range. I simply cannot believe that a human being could absorbs 15 rounds of a 30 caliber projectile and still be among us. That's crazy talk. It's far more believeable that he missed 15 times, rather than the Korean kept charging, oblivious to his wounds.
Consider the 30 carbine has greater velocity and energy @ 100 yards and even @ 200 yards than the vaunted .45 ACP has at the muzzle:
The 30 carbine was responsible for downing tens of thousands of frenzied, banzai enraptured Japanese solders, yet no one questioned it's value at a time when it's effectiveness was under incredible scrutiny.