As RIFLE cartridges go, the .30 Carbine only qualifies because it was designed to be fired from................a carbine. Other than that, it is a medicore pistol cartridge. Using safe industry standard loading data, you can load a .357 handgun to fire the same weight bullet, faster out of a handgun than USGI ball ammo out of a carbine. That is why it isn't a good rifle cartridge. By the way, the .44 Magnum is a pistol cartridge. I realize that you can buy rifles chambered for this cartridge, but it was disigned and built as a pistol cartridge. It is also significantly more powerful than a .30 Carbine. It shoots a heavier projectile that is bigger in diameter with more energy. I am going to make some very general, broad statements that will make the ballistic nuts scream, but..... When you are dealing with fairly slow moving projectiles, they simply punch a hole through the target. The .44 mag puts a big hole through the target. Since the bullets are pretty heavy they penetrate well. Sometimes you can shoot a bullet that expands and makes and even bigger hole. The .30 Carbine works the same way except the hole is smaller, the bullet isn't as heavy, and from what I have read the bullets usually don't expand. Very rough, but simple explanation.
Again, as rifle cartridges go, the 7.62x39 is very mediocre. It isn't particularly fast. It shoots a medium weight bullet with a rainbow trajectory. Yeah it is cheap. Yeah a lot of people have been killed with it. But when comparing rifle cartridges to other rifle cartridges, it is right near the bottom of the performance pile. The reason it is cheap and the reason a lot of people have been killed by it is simply the numbers of them out there. As we all know, prior to the 1970s, this was the standard cartridge of the USSR which gave them out like candy all over the world by the millions. Millions of people shoot at other millions of people and some people get hit and die. That doesn't make it a good cartridge. This is the same reason that the .22LR and .25 ACP have killed so many people. Because a whole lot of people have been shot with them. Because there are a lot of them out there. In addition, the cartridge is small and operates at low pressures, therefore it can be used in small cheap guns that are preferred by people who shoot other people. Shoot enough people and some of them will die. That doesn't make them a good cartridge for that purpose either.
One problem with discussions like this is that some people get their feelings hurt because their faviorite (or only ) rifle cartridge is listed as being not so hot. But, emotions don't change the facts.
The only thing I can think to add is..... 
It Worked!! 204 gets my nod for worthless ( to me), but itching for a inexpensive 17m2 10/22 barrel.
