DENVER: Firearms play an outsized role in the hearts of Coloradans. It's a frontier state that adopted gunslingers Buffalo Bill and Doc Holliday as native sons, where treasured guns are routinely passed from generation to generation.

So when Colorado's Democratic Governor John Hickenlooper made known that he plans to ratchet back gun rights Wednesday by signing two limits into law, Republicans and gun-rights supporters gasped.

Then they set to work trying to undo the new laws to limit most ammunition magazines to 15 rounds and to expand required background checks to private and online gun sales.

At least two ballot petitions had been filed. Some Republicans hinted at lawsuits. More predicted political repercussions for Democrats in a state poised to be first outside the East Coast to put new restrictions on firearms after last year's mass shootings in Aurora and Newtown, Connecticut.

Hickenlooper says he supports gun rights. But a few months after famously saying the Aurora movie theater shooting couldn't have prevented by gun control, the self-described moderate started explaining how his thinking changed.

"When you look at what happened in Aurora, a great deal of that damage was from the large magazine on the AR-15 (rifle). I think we need to have that discussion and say, 'Where is this appropriate?'" Hickenlooper said in a December interview.

The governor didn't ask for a magazine limit in his opening address to lawmakers this year, but he asked for expanded background checks.

"Surely, Second Amendment advocates and gun control supporters can find common ground in support of this proposition: Let's examine our laws and make the changes needed to keep guns out of the hands of dangerous people," Hickenlooper said.

Lawmakers sent him both, plus a measure to revive fees for gun purchasers needing background checks. Both become effective July 1.

When Hickenlooper signaled he'd sign them all, reaction was swift. A suburban Denver gun-accessories maker, Magpul Industries, said it would make good on a threat to leave the state.

"It is disappointing to us that money and a social agenda from outside the state have apparently penetrated the American West," the company said in a statement.

Republicans were angry and saddened, too. The party's lawmakers have tried and failed to expand gun rights in reaction to the mass shootings. They said Monday that the governor's careful reputation as a moderate compromiser was in danger.

"If he signs these bills, I have to come to the conclusion that he's more interested in his national prospects than he is his legacy here in Colorado," said Republican Sen. Greg Brophy, who represents a rural part of the state's eastern plains. "These are not moderate. These are extreme, and just really unpopular."

Other Democratic gun control proposals are pending in the state Legislature - including a ban on gun ownership by people accused of domestic-violence crimes and a measure to eliminate online-only safety training for people seeking concealed-weapons permits - but haven't attracted the opposition of the magazine limit and the expanded background checks.

Republican gun ideas were hastily rejected earlier this year. Those ideas included expanding gun laws to allow teachers to carry concealed weapons, and a failed attempt to require armed security guards at businesses that ban concealed weapons.