One of the most controversial gun-control bills introduced in California this year — a move to seize the 166,000 registered assault weapons grandfathered in under the state’s ban — is dead, its author said Thursday.

When Assemblyman Rob Bonta, D-Oakland, introduced AB174 in January, it was designed to declare the Legislature’s intent to end all “grandfather clauses” allowing ownership of assault weapons and large-capacity magazines. But on Tuesday, he gutted and amended the bill to address public-school health centers instead. Coincidentally, it was the same day that U.S. Senate Majority Leader Harry Reid announced he won’t include Sen. Dianne Feinstein’s proposed reinstatement of the federal assault weapons ban in the gun-control bill he brings to the floor.

Bonta said Thursday that he came to realize his proposal was a nonstarter.

“It would be extremely expensive, for one — if you were going to take back guns that were grandfathered in, you would have to provide market compensation for them,” he said. “I didn’t think that made the most sense from a fiscal perspective.”

Australia in 1996 and 1997 bought back about 640,000 newly banned semi-automatic rifles, semi-automatic shotguns and pump-action shotguns at an estimated cost of at least $320 million. There was no registry to work from, however, and by some estimates as many as 40 percent of gun owners didn’t comply with that mandatory buyback.

Bonta also said he was keenly aware of the gun lobby’s assertion that any state or national registration of firearms is merely a prelude to confiscation — something his bill actually pursued.

“I didn’t want to have a bill that plays into that argument,” he said. “I wanted to concentrate on some other bills that I thought would be more focused and more effective.”

Bonta’s other gun-control bills include AB187, a 10 percent tax on ammunition sales to fund crime-prevention efforts in violence-wracked California cities; AB180, giving Oakland special dispensation to enact gun regulations more strict than the state’s; and AB1020, requiring the state to notify gun buyers during their 10-day waiting periods that “straw purchases” on behalf of those banned from owning guns are illegal.

California enacted its assault weapons ban in 1989 and expanded it in 1999, but those who already owned the banned guns were allowed to register and keep them.

Josh Richman covers politics. Contact him at 510-208-6428. Follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics.