would a 30 cal carbine be enough knock down power for whitetails?

With factory loadings they only produce around 800-900 foot pounds of energy and that is at the muzzle. So I would say no. I also wanted to use this round/gun for a quick handling deer rifle, but was cautioned otherwise.

I've known a number of people to kill deer with them, but I'd put the 30 carbine in the .357 magnum pistol's class. In my opinion 100 yards at the absolute maximum.

If you are looking for something fast, get a pump gun or a lever gun, and leave the carbine at the range. Fun gun to play with, not enough for deer IMO.

The M-1 carbine is not a good round for hunting any big game and that includes deer.....it's a fun round for a lot of sand pit games and that's it limitations.....

I have a friend that let his duaghter shoot a deer with one last year and the deer ran off and was killed the next day by someone else we went to look and found the bullet had just broken the shoulder blade and never went in the body cavity . That is at 50 yards !!! Not enough gun in my opinion

I would have to say probably not a good choice. If I had to guess on the result the story would go just as Danthehunter described.

What gun is it? Mini-30? Lever action ruger?

That round is a popular round for blocking trail for pigs here in hawaii. If you hit the animal in the "drop them in their tracks area" (spine/vertibrae)then they will drop in their tracks. If you hit them in the lungs, I'm sure they will go down too within a reasonable distance... maybe not, I have no experience. But it is a short range gun. A good gun for still hunting in thick cover but a horible round for shooting long distance such as over fields. 100 yards would be a far shot for one but you probably could still crack the spine and drop them even at that distance. I wouldn't shoot for the lungs over 75 yards. Not that I know what I'm talking about or nothing because I've never used one but they are one of the most popular rounds down here for pigs out of a mini-30.

The gun in question is the military M1 claiber .30 carbine.
A Mini 30 shoots the Russian 7.63x39 which is on par with a 30-30 Win. round in terms of power and could be a great close-up "pig" round

I consider the 30-30 to be a 150 yard gun at max! The .30 carbine would be way under powered! Go with something better!