House Speaker Mark Ferrandino, D-Denver, promised unlimited and unfiltered opportunities for comment, saying: "If it takes two hours, that's great. If it takes 20 hours, that's great. I don't want to allow the shutting of people's ideas and opinions."
Members of the House, who typically adjourn at noon Fridays, were advised to prepare to be in the chamber until early Saturday, KMGH-TV, Denver, reported.
At issue are four gun control bills, the toughest battle expected to be over one that limits ammunition magazines to 15 rounds. The Democrats have a 37-28 majority in the Colorado house, with predictions that at least four Democrats will vote against the measure, The Denver Post reported.
Other proposals would ban concealed firearms on college campuses and require background checks for prospective gun owners.
In an 11th-hour attempt to kill the measure banning high-capacity ammunition magazines, Alfred Manufacturing, a manufacturer of the magazines with headquarters in Denver, announced the company will leave the state if the measure passes. It followed a similar threat from Magpul, Colorado's largest maker of high-capacity magazines.
Republican leadership said it would present the letter from Alfred on the House floor.
Much of the early debate Friday centered on a section of the high-capacity magazine bill that clarifies manufacturers in the state can sell their products to out-of-state and U.S. military customers, a response to the threat by the local firms, the Post reported.
The measure is sponsored by Rep. Rhonda Fields, D-Aurora, who pointed out the mass shootings that employed high-capacity magazines.
"Is there any study out there that shows a ban on high-capacity magazines prevent shootings or save lives? I don't think there is, in fact there isn't," responded House Minority Leader Mark Waller, R-Colorado Springs. "We're going to pass this legislation for no other reason, none, zero, than to feel good."
Legislation will be considered by the state Senate if it passes the House.