Getting exact numbers is difficult because not every gun has to be registered and many that should be aren't. The government estimates there are more than 300 million guns in America.

A recent Gallup poll shows nearly half of all U.S. households have at least one. Click here to view the study on There are about 114 million handguns, the easiest to carry and conceal; 110 million rifles, often grouped in the category of "assault-style weapons;" and 86 million shotguns, that fire shells containing metal pellets.

One of the major issues surrounding the debate is how much ammunition guns can fire, as well as how fast it can be fired.

Most gun crimes in America are committed with semi-automatic pistols (seen below). Semi-automatic means every time you pull the trigger a bullet will fire until your magazine is empty. Rifles can also be semi-automatic (seen below); again, one pull fires one bullet.

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Semi-automatic pistolSemi-automatic rifleAutomatic rifle

With a fully automatic weapon like a machine gun (seen above), you pull the trigger one time and hold it. It will fire every bullet in your magazine until it is empty. Fully-automatic machine guns are considered military weapons. They’re highly regulated and hard to find. Click here for a photo gallery that shows and explains the different types of guns.

The mass shootings in Aurora, Colorado and Newtown, Connecticut have renewed calls for new regulations on guns and ammunition.

They also prompted a gun violence summit in January at Johns Hopkins University. Twenty experts from the U.S. and other countries presented research and offered solutions.

Daniel Webster, John Hopkins University Center for Gun Policy

Daniel Webster (pictured at left) of the Johns Hopkins Center for Gun Policy took part in the discussion. "We think we have a set of recommendations that not only will be effective in reducing gun violence in America, but will be constitutional and have wide support with the public and gun owners," Webster said at the meeting. "We need to fix our system of background checks. It is really indefensible that we have a system that allows people to sell firearms with no background checks, no record-keeping and no accountability."

Among the panel's other recommendations: universal background checks for all gun buyers, setting a minimum age of 21 for all handgun purchases or possession and restricting anyone with a violent misdemeanor record from buying guns for 15 years. Finally, on the big issue of gun bans, this expert panel recommends banning future sales of assault-style weapons and large-capacity magazines that hold more than ten bullets.

DON REIMER The possibility of government action has many gun owners up in arms; it has also created a run on guns according to gun store and range owner Don Reimer (pictured at right). "There's panic buying going on, both in ammunition and guns," he said. "Instead of going to the store and buying hundreds of rounds, [they] buy thousands."

Sales of guns and ammunition are at all-time highs. The FBI says in 2012, more than 19.5 million background checks were performed -- almost 2.8 million in December alone. Click here to view a PDF of the study on background checks at

Gun and ammo maker Brownells, Incorporated said in a December 2012 forum post on that it sold three-and-a-half years' worth of magazines in just 72 hours. Click here to view the post.

While much of the public attention is on assault-style weapons, the fact is they are not used in most gun crimes, including murders. The FBI's latest uniform crime report shows of the 12,664 murders in 2011, 8,583 involved firearms. Click here to view that study on Handguns were used in 6,220 of those, just over 72 percent of the total. By comparison, rifles were involved in 323 murders, about four percent. Shotguns were involved in 356, also about four percent. About 1,700 other murders, the other 20-percent are listed as using "unspecified guns."

GARY KLECK Florida State University criminology professor Dr. Gary Kleck (pictured at left) has researched gun violence for decades. He says data is clear on the most deadly weapons. "The most common gun used in murders is a handgun, and the most common handgun used these days would be a semi-automatic 9mm pistol," he explained. "They would rarely involve large-capacity magazines and certainly assault weapons have nothing to do with the violence problem in America."

Kleck says his research shows the need for more thorough background checks for felons or the mentally ill, plus an enhanced licensing system.

We asked Dr. Kleck if other gun restrictions, including bans, would reduce gun crime. "For the most part, most gun controls don't work. Registration doesn't work, waiting periods don't work," he responded.

DON KATES Kleck and colleague Don Kates (pictured at right), a retired criminal law professor and NRA member, have similar findings on gun restrictions. "They work with law-abiding people, but law-abiding people, you don't need them for. They don't work for criminals," he said.

That's a sentiment shared by UCLA law professor Eugene Volokh (pictured below), an expert on firearm regulation. "Even if you somehow managed to politically enact a total ban on guns, there would be many, tens of millions, left out there that American criminals would find very, very easy to get their hands on," he said.

EUGENE VOLOKH While lawmakers consider if any steps should be taken, one thing is certain: the heated public debate over guns in America will rage on long after Congress makes its decision.

A recent Associated Press poll shows almost 60 percent of those questioned want tougher gun laws, while 35 percent say they shouldn't be changed. Five percent say they should be loosened.

Here are more facts to the gun story -- Dr. Kates says personal protection often gets overlooked. He says there are three million incidents each year where a person is able to prevent themselves from being hurt or killed because they have a gun.

Finally, the largest number of gun-related deaths is suicides. Guns were used in about half of all suicides in 2011 according to the CDC. There were over 38,000 suicides that year. 19,392 of them involved a gun.