Family members of Gabe Zimmerman, the congressional staffer who was on e of six killed during January's mass shooting in Tucson, were on Capitol Hill Tuesday calling for a ban on high-capacity ammunition clips.

Zimmerman's fiancée, Kelly O'Brien, and his father, Ross Zimmerman, spoke at a press conference to support Senate and House bills that would ban assault clips.

"I do not own a gun, but I respect every American's constitutional right to have a gun." O'Brien said to the gathering of reporters. "However, every constitutional right comes with responsibility."

Rep. Carolyn McCarthy, D-N.Y., and Sen. Frank Lautenberg, D-N.J., have authored bills in the House and Senate that would limit the number of bullets a magazine could contain.

"It is entirely reasonable to limit gun magazines to 10 bullets as Rep. McCarthy and Sen. Lautenberg are proposing," O'Brien said. "Ten bullets are more than enough for self defense which is why many people own a handgun."

Ross Zimmerman, suggested that allowing high-capacity magazines to remain legal is irrational.

"What is so hard about the idea of common sense responsible behavior?" he asked. "What is so hard about banning something like this? It is a small piece of a much larger picture. I have plenty of friends who own guns, none of them thinks these things are reasonable."

But the National Rifle Association says the high-capacity clips are rational. In a post on its website a few days after the Tucson shooting, the NRA defended the magazines.

"Law-abiding private citizens choose [the magazines] for many reasons, including the same reason police officers do: to improve their odds in defensive situations," the post said.

The Brady Campaign to Prevent Gun Violence released a new television ad about assault clips to coincide with Tuesday's press conference.