The Gun Debate: What makes a gun an assault rifle?

President Obama on Wednesday announced support for a new ban on military-style assault weapons, further frustrating critics who say the term itself is misleading and based on cosmetics -- not carnage or crime.

"The number one myth is these are machine guns. They're not machine guns. They're semi-auto, meaning I pull the trigger one time, I get one bullet," said Jeff Serdy of AJI Sporting Goods near Phoenix.

Serdy is among those who claim the features that allow these guns to qualify as "assault" weapons have little to do with how deadly they are. They include "a telescoping stock, pistol grip, ability to accept a magazine, and a flash-hider."

He said: "This AR-15 is no more dangerous than this hunting rifle which is used for woodchucks all across the East."

A bill similar to what Obama is calling for is expected to be introduced soon by Sen. Dianne Feinstein, who also helped author the last assault-weapons ban that expired in 2004. The National Academy of Sciences determined that effort had "no clear impact on gun violence," though groups like the Brady Campaign to Prevent Gun Violence say the ban did have some impact on crime.

But Feinstein's new bill reduces the allowable number of "military characteristics" from two to one and does not allow gun makers to include cheap work-arounds like flash suppressors and bayonet lugs. The result is a proposed ban that could be more sweeping.

It also bans any magazine whose capacity is greater than 10 rounds and 'bullet buttons" -- which are simple devices used to allow an owner to quickly change magazines.

Gun control advocates say those changes will make the new bill more effective.

"The combination of improved and expanded background checks, effective bans on assault weapons and high-capacity ammunition magazines, and stronger anti-trafficking laws will work together to prevent another Newtown and to stem the daily gun violence that tears apart too many families and communities," according to a statement released Wednesday from the Violence Policy Center.

The new Feinstein bill will also specifically ban 120 weapons, including the popular AK-47 and AR-15, often called the Barbie Doll of guns because it is so easily accessorized. The AR-15 is the most popular gun sold in the U.S. today, with almost one-half of users saying they use it for target shooting.