Just based on book knowledge only... it depends. I think that 9mm is only used for pistols and maybe submachineguns, which are less powerful. The M-16 is 5.56, and I've heard reports from Iraq of the enemy being shot several times and keeping on coming. On the other hand, the Vietnam-era M-16s had a barrel with a more gradual turn of the rifling in the barrel, so the round wasn't as stable when it hit someone, and caused a worse wound. I'd guess that all other things being equal, 7.62 is heaviest and so would be the deadlist. But there's a big diff between the muzzle velocity of an AK-47 and an M-1 from WW2. Also, of course in real life you have to take into account other things like being able to carry twice the number of 5.56 rounds as 7.62, the weight of the weapon, etc.

It all depends on where the bullet impacts the body. You could be hit by a cannon that merely grazed your skin and suffer minimal damage. There is on record an elephant being killed by a .22 rifle (shot in the stomach, died of peritonitis many days later). The 5.56mm is the current round used by the US military. They seem to kill lots of people with that round. The 7.62 is also .30 caliber. The US used a .30 caliber in WWI, WWII and Korea. Again lots of people killed (I realize the 7.62 military round is different from the .30 caliber round used in the wars just mentioned). There were some rifles chambered for a 9mm rifle cartridge and used in WWII and some other wars. The caliber never was greatly popular as a military round. The 9mm most discussed is a pistol cartridge which was used in WWII and is quite popular today. Since it is a pistol cartridge, its number of "kills" is probably way below the number of kills attributed to the other calibers. But we still have to ask, where is the bullet impacting the body. Any of these cartridges can kill if the victim is hit in the right place from a close enough distance that the bullet has the required energy to cause a killing wound.

Depends on where you get hit (I'm assuming one round only here), and the distance. Overall a 7.62 will have a greater impact than the other two types. 9MM is really designed more for the user than the use-ee (target), as is 5.56. Lighter to carry, and you can control the weapon more that with most 7.62 weapon. Also, you have variations on the different rounds.

Id say the one that hits you in the head or heart is the worst one....

this question is also a relative question for that the distance required to to inflicked a kill. a kill witth a 9mm pistol bullet could only be done under 25meters and with the 5.56 and 7.62 are rifle rounds. if you were to be hit by either of these rifle rounds would be deadly under 1000yd, the 5.56is the standard round for nato it goes into all m-16s ar-15, where as the 7.62 is a heavier bullet used in sniper rifles, 700 series remigton 308cal, that round was also used in the m-60 medium belt type machine guns. the 9mm is used in submachine guns and pistols and is not in the same class as the, rifle rounds of 5.56 and the 7.62. where as the 7.62 is heavier than 5.56 they are both deadly at 400rds or better, the 7.62 could shoot a little farther with a heavier bullet thats about all i can tell you i hope the answer you were looking for could be found in my response, or a least give you a better idea.

7.62 deadly 9mm is a bb gun after 100 meters, i would not want to get shot by any one but if that were to happen 9mm at 100m wil kill you but will more than likley hurt you. the most deadly is the 7.62, and 5.56 is a nato round and is acuurate up to 1000 yds and deadly in the hand of a marksmen but really has no kick they are a small hot round but becuase it is so small when it hits something it slows down right now. where as a 308cal 7.62 is used on m-60 machine gun has a little more weight and powder you could shoot some one behind a 12inch tree and you could take on a helicopter at real close range as compared to what i shoot the browning BAR my 338, and my 7mmrem mag make both of them other caliburs relativley small,

I don't know. Why don't you try one of each, and see which one you liked best.