The legislation thrust Colorado into the national spotlight as a potential test of how far the country might be willing to go with new gun restrictions after the horror of mass killings at an Aurora movie theater and a Connecticut elementary school.
Democratic Gov. John Hickenlooper signed bills that require background checks for private and online gun sales and ban ammunition magazines that hold more than 15 rounds.
The debate in the Democratic-controlled Legislature was intense, and Republicans warned that voters would make Democrats pay. The bills failed to garner a single Republican vote.
The bills' approval came exactly eight months after dozens of people were shot in Aurora, and a day after the executive director of the state Corrections Department, Tom Clements, was shot and killed at his home. Hickenlooper signed the legislation right after speaking with reporters about Clements' slaying.
Hickenlooper said large-capacity magazines "have the potential to turn killers into killing machines." He also said he realized some gun owners may be inconvenienced but that "the potential for damage seems to outweigh, significantly, the inconvenience that people would have," he said.
The bills signal a historic change for Democrats in a state where owning a gun is as common as owning a car in some rural areas.
"He just slapped rural Colorado right in the face," said Republican Sen. Brophy, who represents an eastern plains district. "They are overwhelmingly upset about this."
Both bills take effect July 1. People who currently own larger-capacity magazines will be able to keep them.
At the signing ceremony, Hickenlooper was surrounded by lawmakers who sponsored the bills, and relatives of mass shootings. Hickenlooper also signed requiring buyers to pay fees for background checks.
Each time he signed a bill, applause erupted from lawmakers and their guests, who included Jane Dougherty, whose sister was killed in the attack at Sandy Hook Elementary in Newtown, Conn.; Sandy Phillips, whose daughter was killed in Aurora; and Tom Mauser, whose son was killed in the 1999 Columbine shooting in Colorado.
Phillips, who lost daughter Jessica Ghawi, reminded Hickenlooper that it was the eight-month anniversary of the theater rampage.
"You've given us a real gift today," she told the governor.
Later, Phillips added: "Thank you so much. You're leading the entire country."
Dougherty thanked Hickenlooper with tears in her eyes. Mauser also expressed gratitude.
"I knew it would be a long haul," he said. "But I had faith in the people of Colorado."
Democratic Rep. Rhonda Fields, who represents the district that includes the Aurora theater, said the governor had signed "common-sense legislation."
"Gun violence is a problem nationwide, and sadly in the state of Colorado, we are all too familiar with some of these tragedies," Fields.
Lawmakers debated firearms proposals after the Columbine High School shooting, and began requiring background checks for buyers at gun shows. But nothing they did then was as sweeping as the proposals they took up this year.
This year, Colorado lawmakers succeeded while members of their party stumbled in other states.
Washington state's Democrat-controlled House failed this month to pass a universal background check bill. A bill requiring background checks at gun shows in New Mexico also stalled in that Democrat-led Legislature.
Republicans have warned that voters will punish Hickenlooper and other Democrats who voted in favor of the measures.
"The real solution here is at the ballot box in 2014," Brophy said.
Republicans have said limiting magazine sizes will drive jobs from the state, and ultimately won't prevent criminals from getting larger magazines in other states.
One Colorado-based manufacturer of ammunition magazines disclosed plans to relocate because of the new restrictions.
Police chiefs in urban areas supported the bills, but some rural county sheriffs opposed the new background checks, arguing the move is unenforceable and endangers Second Amendment rights.
Hickenlooper said law enforcement should try to find common ground.
"This shouldn't be rural versus urban. We are one state," he said.