Brennan Linsley, Associated Press
In this July 20, 2014 photo, shooters practice with pistols at the gun range at Dragonman's, a gun dealer east of Colorado Springs, Colo. As more expansive gun background checks are set to take effect in Washington state, law enforcement agencies, gun groups and others are waiting to see exactly what impact the new law will have.

OLYMPIA, Wash. — As more expansive gun background checks are set to take effect in Washington state, law enforcement agencies, gun groups and others are waiting to see exactly what impact the new law will have.

Initiative 594, which passed this month with 59 percent of the vote, requires background checks on all sales and transfers, including private transactions and many loans and gifts. There are some exceptions, including transfers between family members and antiques produced before 1898.

When the new law takes effect Thursday, Washington will join six other states — California, Colorado, Connecticut, Delaware, New York, Rhode Island — plus Washington, D.C., that currently require universal background checks for all sales and transfers of all firearms, according to the National Conference of State Legislatures.

About a dozen other states have varying laws on expansion beyond what federal law requires.

Once I-594 takes effect, personal transactions that do not already involve a dealer would require a background check, and the person selling or transferring a firearm would either need to meet the potential buyer at a licensed dealer, who would run the check, or, if the seller were shipping the firearm, they would ship it to a dealer in the city where the potential buyer lives.

Mitch Barker, executive director for the Washington Association of Sheriffs and Police Chiefs, said he's heard concerns about possible increased workload for the local law enforcement agencies that run the background checks.

"None of us will know until we get up and running," he said.

The FBI's National Instant Criminal Background Check System processed more than 560,000 firearm background checks in Washington state last year, and has processed more than 388,000 between January and the end of October of this year, according the agency's online report.

How many more checks might actually occur is hard to predict, since the size of the private market in the state is unknown.

However, a state Department of Licensing projection based on Colorado's experience with expanded checks that estimated that checks for private sales and transfers would make up about 2 percent of all checks conducted in the state: about 13,440 new background checks in Washington state through July of next year.

That estimate grows to 35,481 new checks for the 2015-17 biennium, and to 51,093 for the 2017-19 biennium.

"Responsible gun owners aren't going to see a difference," said King County Prosecutor Dan Satterberg. "What it might do is raise the risk for people who are willing to sell guns, no questions asked."

But opponents say that people will still find a way to get guns without background checks.

"The guy who is a convicted felon who knows he can't have a gun is going to get it anyway," said Don Teague, the owner of a Private Sector Arms in Olympia.

Under current state law, anyone buying a gun from a licensed dealer has to go through a background check. That check screens the buyer to make sure they aren't a felon, a fugitive, or in the country illegally, among other disqualifiers. Private sales and transfers don't currently require a background check under state or federal law.

Starting Thursday, many gifts and loans that previously didn't require a background check also will have to have one. The measure includes exceptions for emergency gun transfers concerning personal safety, gifts between family members, antiques and loans for hunting.

Opponents had taken the most issue with language that requires checks on transfers. A rally is scheduled at the Capitol on Dec. 13 where protesters plan to openly exchange guns.

Barker, the executive director of the sheriffs and police chiefs association, does not believe that handing a gun to someone else violates the initiative, but he said that eventually the state attorney general will likely be asked for clarification.

As for how to enforce the law, Barker said that's a bit trickier.

"If somebody committed a crime with a firearm, and if the source was tracked back to someone who didn't do a background check of the person who they transferred the gun to, that to me would seem to be the most likely scenario where a law enforcement official would take action," he said.

Under I-594, a person who knowingly violates the law could be subject to a gross misdemeanor; a knowing violation twice or more is a Class C felony.

Washington Arms Collectors, which organizes gun shows for its members across the state, recently announced it was working with dealers at its shows to offer $10 background check fees.

"We're trying to find ways to implement it and trying to find ways to implement it that are most cost effective for the members," said Phil Shave, the group's executive director.