the guns are originally purchased by law abiding citizens who then sold them in the streets wich turn them into illegaly purchased weapons that the right wing like to use as an argument as to why banning guns doesn't solve anything.

Although the sale of handguns is illegal in Chicago, the city is ringed by a handful of gun shops, some just blocks from the city limits. Altogether, there are 441 federally licensed dealers in suburban Cook County and the five collar counties, according to the latest ATF data. Most of these suburban shops, officials say, are law-abiding businesses that operate responsibly. But a small percentage—fewer than 1 percent, the city says—are responsible for nearly half of all the firearms used in crimes in Chicago. Similarly, a small group of wholesalers are the principal suppliers of these so-called dirty dealers; 6 percent of wholesalers furnish 79 percent of all guns used in crimes in the city, according to information from the ATF's National Tracing Center.

One south suburban store, for example, is especially notorious. In a recent four-year period, according to analysis of ATF figures by the Washington, D.C.–based not-for-profit Americans for Gun Safety Foundation, Chuck's Gun Shop in Riverdale sold more guns linked to crimes than any other licensed gun dealer in the nation. Citing ATF records, the group reported last January that Chuck's sold 2,370 guns between 1996 and 2000 that were recovered by police and traced to crimes. (The shop's manager, John Riggio, says of the report, "You can do a lot of things with numbers. That's all I'm going to say.") Thirteen other gun dealers in the state—all but two were from Chicago's suburbs—were ranked by the  Americans for Gun Safety Foundation among the top 120 dealers nationwide in supplying guns to criminals. Seven northwest Indiana gun shops also made the list.

The most common sources of guns used in crimes, the ATF reports, are "straw purchasers," individuals with valid firearm owner's identification cards who have passed criminal background checks and can buy guns legally, but do so on behalf of others. In most straw-purchase situations, Mike Smith says, a shill—typically a drug user, perhaps a family member or girlfriend with a clean criminal record—buys a gun and either gives it or resells it to someone else. Prohibited purchasers are mainly convicted felons, gang members, drug dealers, and juveniles.

http://www.chicagomag.com/Chicago-Magazine/June-2004/Biography-of-a-Gun/index.php?cparticle=2&siarticle=1

The bold part of the article speaks volumes though ...

It should be (relatively) trivial to stop straw purchases by simply cracking down on individuals who sell guns illegally. If someone bought a gun legally, they should still have the gun or have the paperwork to demonstrate that they sold it legally. Audit people who have bought an unusual number of guns and if they can't demonstrate that they have the weapon or that it was sold legally send them to prison.

So you're telling me you could kill someone? Also, most of the time you can use whatever is at hand to fight a burguler.

where's does the constitution define the line between murder and lawful gun ownership?

Where does the constitution define the line between murder and lawful knife ownership?

Where does the constitution define the line between murder and lawful baseball bat ownership?

Murder is the act of killing another individual, and a person is just as dead if they're killed by a knife or a gun. If you want to lower murder rates you reduce the number of people with motive to kill other individuals, you don't arbitrarily ban guns, knives, basball bats, or martial arts.

I knew that knives and bats kill too, just like guns. These things oviously happen for other reasons, like economic or social reasons, just help those people, it's amazing how America's is the richest, most powerful country in the whole world yet so many live in poverty, yet so many live in prison among other serious problems, yet it is so respected in this world. What's amazing is it's so rich but so in debt it can't even help it's own people, they don't feel apart of society, so they commit crimes to do, even if it's murder, they just show up. This sort of thing, shows the major flaws in capitalism.

as you can see most of the guns used in crimes are purchased legally originally, so your point was wrong, also if stoping straw purchasers was so trivial they would have done it already. Also for the bold even if a minority is responsible for the majority of the crime related gun sales those guns are still sold legally.

On the point of the drug cartels the ATF estimate that 70% of the guns used by them come from the US but I cannot stated if they were originally purchased legally tho, but I suppose a good portion was.