There are four basic reasons for the second ammendment in the United States.
Every one of the founding fathers is on record to the effect that private ownership of firearms, the 2'nd ammendment, is there as a final bulwark against the possibility of government going out of control. That is the most major reason for it.
At the time of the revolution and for years afterwards, there were private armies, private ownership of cannons and warships. . . The term "letters of marque, and reprisal" which you read in the constitution indicates the notion of the government issuing a sort of a hunting license to the owner of a private warship to take English or other foreign national ships on the high seas, i.e. to either capture or sink them. The idea of you or me owning a Vepr or FAL rifle with a 30-round magazine is not likely to have bothered any of those people.
The problem with drug-dealers owning AKs is a drug problem and not a gun problem. Fix the drug-problem, i.e. get rid of the insane war on drugs and pass a rational set of drug laws, and both problems will simply go away. A rational set of drug laws would:
1. Legalize marijuana and all its derivatives and anything else demonstrably no more harmful than booze on the same basis as booze.
2. Declare that heroine, crack cocaine, and other highly addictive substances would never be legally sold on the streets, but that those addicted could shoot up at government centers for the fifty-cent cost of producing the stuff, i.e. take every dime out of that business for criminals.
3. Clamp a permanent legal lid down on top of anybody peddling LSD, PCP, and/or other Jeckyl/Hyde formulas.
4. Same for anybody selling any kind of drugs to kids.
Do all of that, and the drug problem, the gun problem, and 70% of all urban crime will vanish within two years.
But I digress. The 2'nd ammendment is there as a final bulwark against our own government going out of control. It is also there as a bulwark against any foreign invasion which our own military might not be able to stop.
Admiral Yamamoto, when asked by the Japanese general staff about the possibility of invading the American homeland, replied that there were fifty million lunatics in this country who owned military style weaponry, and that there would be "a rifle behind every blade of grass". This apparently bothered him a great deal more than the 200,000 or so guys in uniform prior to the war.
A third obvious reason for private ownership of firearms is to protect yourself and your family from criminals and wild animals. In fact, the second amendment is basically an idea whose time has come all over the world. Why on Earth should people in India tolerate having 80,000 of their number killed every year by snakes? That could simply not happen in a nation whose people were armed.
And there's a fourth reason for the 2'nd ammendment, which is to provide the people with food during bad economic times. When you listen to people from New York and from Texas talk about the depression of the 30's, you hear two totally different stories. The people in New York will tell you about people starving and eating garbage, and running around naked. The Texans (and others from more rural areas and places in which laws and customs had remained closer to those which the founding fathers envisioned) will tell you that while money was scarce, they always had 22 and 30 calibre ammunition, and that they always had something to eat, even if it was just some jackrabbit.
Eating is habit forming. In any sort of a down economic situation, that fourth rationale for the second amendment quickly becomes the most important.