The plan would forbid the future sale of ammunition magazines that hold more than 10 rounds.
Nicole Hockley says she's not a political person or a lobbyist.
She's the mother of Dylan, who was murdered last December in his classroom at Sandy Hook Elementary, in Newtown, Connecticut.
The shooter, she says, used 30-round magazines.
"He chose to leave his smaller capacity magazines at home. He chose to have the best kill rate possible by using his high-capacity magazines, which only exist to spray as many bullets as possible in the shortest timeframe without reloading ... In an instant, my precious boy was gone and so was everyone else." -Nicole Hockley
Hockley told Senators that what happened in Newtown could happen in Illinois, but banning the sale of high-capacity magazines would help to prevent it.
"You are taking an action to prevent your own Newtown."
Jay Keller represents Illinois companies that make guns. He says to prevent tragedies, lawmakers need to broaden their focus, and improve mental health services. Keller says manufacturers will move out of state if the measure passes.
"A magazine ban is a knee-jerk reaction that fails to address the underlying societal problems." -Jay Keller
Gun-owners would be allowed to keep magazines they already have.
Amanda Vinicky contributed to this report.