Colorado voters appeared poised to enact a 6.5 percent excise tax on firearms and ammunition on Tuesday, joining California as one of two states to impose special taxes on gun sales.

The 6.5 percent tax is expected to generate $39 million a year to fund a range of mental health programs and support services for victims of crime, some of which are at risk of running out of money.

Proposal KK he received 54 percent of the vote by 11:40 p.m., and his supporters declared victory late Tuesday. The Associated Press had not yet called the race at that time.

The measure was sent to a vote earlier this year by the state legislature’s Democratic majority. Supporters saw it as a way to force gun owners, dealers and gun manufacturers to step in to cover some of the social toll of gun violence, while opponents saw it as an affront to the right to bear arms under the Second Amendment.

“Tonight is truly a full-circle moment for me,” House Majority Leader Monica Duran, D-Wheat Ridge, said in a statement. “Without the support of crime victim services, as a young single mother caught up in an abusive relationship, I would not be able to be here today celebrating the passage of Prop. KK.”

If it passes, most Colorado firearms dealers, gun manufacturers and ammunition sellers would have to pay a 6.5 percent excise tax on eligible sales starting April 1.

That’s $33 in new taxes on a $500 handgun, or $65 in taxes on a $1,000 rifle; $20 worth of ammo would cost an extra $1.30. Much of these costs would likely be passed on to consumers.

The tax would also apply to many gun parts and accessories, as well as equipment used to manufacture firearms.

It would not apply to companies with annual sales of less than $20,000. Purchases of weapons by law enforcement agencies, as well as by police and military officers on duty, would be exempt. Private sales from one person to another would also not be taxed.

Currently, guns and ammunition sold in Colorado are subject only to state and local sales taxes, as well as a 10% to 11% federal excise tax.

Most of the money generated by the tax would go to the Colorado Crime Victim Services Fund, a grant program that has been shrinking for years as federal funding to support crime victims dries up. Most of the services provided through the grants are administered by nonprofit organizations such as the Colorado Coalition Against Domestic Violence, Colorado Legal Services and the Tennyson Center for Children.