SACRAMENTO — It will soon be harder to buy ammunition in California and illegal to own magazine clips that hold more than 10 rounds under a suite of gun-control bills Gov. Jerry Brown signed into law on Friday.

Brown signed six bills and vetoed five, actions that will nonetheless build upon the state’s arsenal of gun control laws aimed at curtailing mass shootings and keeping weapons and ammunition away from the wrong people. California already has the strictest gun laws in the nation.

Many of the 11 gun bills that landed on the governor’s desk this week were crafted in response to the mass shooting in San Bernardino in December, and got a boost of urgency following the mass shooting in an Orlando nightclub last month.

The new laws include SB880 by Sen. Isadore Hall III, D-Compton (Los Angeles County), and Sen. Steve Glazer, D-Orinda, which expands the definition of assault weapon to include specified guns with military-style features capable of accepting any type of detachable magazine. Another bill signed by the governor bans so-called “bullet buttons,” a tool developed by gun manufacturers that allows magazines to easily detach for rapid replacement.

Brown also signed SB1446 by Sen. Loni Hancock, D-Berkeley, which makes it illegal to possess magazines that hold more than 10 rounds of ammunition. The sale or manufacturing of large-capacity magazines was already illegal in the state.

Among the vetoes was the only bill with bipartisan support, AB1176, which would have authorized a ballot measure asking voters to make it a felony to steal a gun or buy a stolen gun, regardless of its value.

The new restrictions led by California’s Democratic-controlled Legislature come on the heels of gridlock over gun control laws in Congress, where House Democrats staged a sit-in to protest last month.

“My goal in signing these bills is to enhance public safety by tightening our existing laws in a responsible and focused manner, while protecting the rights of law-abiding gun owners,” Brown said in a signing message Friday.

All of the bills except AB1176 were opposed by Republicans and gun rights advocates.

“These are constitutionally illegitimate laws passed by a patently illegitimate government that had the audacity to attack and criminalize millions of its own people in Stalin-esque fashion,” said Brandon Combs, president of the Firearms Policy Coalition, a gun rights group.

Whether Californians want the state’s gun-control laws to go further will be left to voters in the fall.

Brown said he vetoed AB1176, the gun-theft felony bill, because it is nearly identical to parts of Proposition 63, Lt. Gov. Gavin Newsom’s “Safety for All” ballot initiative, which will appear on the November ballot.

But the governor signed SB1235, the ammunition background check bill, which also overlapped with Newsom’s ballot measure. SB1235 requires background checks for people buying ammunition, a license for people selling bullets and purchasing data submitted to the state Department of Justice. Newsom’s measure also requires background checks, vendor licensing and data sharing on ammunition purchases, although regulated differently.

Senate President Pro Tem Kevin de León, D-Los Angeles, urged Newsom to withdraw his measure while the Legislature worked to pass the gun control legislation. Newsom declined before Thursday’s deadline to remove measures from the fall ballot.

De León’s ammunition bill, SB1235, however, was amended recently so that if signed by the governor, as it was Friday, parts of it would supersede Newsom’s ammunition proposal should voters approve it.

Newsom’s ballot measure still contains several gun control provisions that the gun lobby is fighting, including requiring gun owners to report when their firearm is lost or stolen.

“Voters will finally have a chance to take matters into their own hands and keep the momentum going with bold reforms that build on these achievements and go well beyond,” Newsom said in a statement.

Melody Gutierrez is a San Francisco Chronicle staff writer. Email: mgutierrez@sfchronicle.com. Twitter: @MelodyGutierrez

Gun bills signed:

SB1235: Requires background checks for people who want to purchase ammunition, licenses for sellers of ammunition and sales data to be collected.

SB880: Expands the definition of “assault weapon.”

AB1511: Limits who a gun owner can lend their firearm to.

SB1446: Prohibits the possession of magazines that hold more than 10 rounds.

AB1135: Bans so-called “bullet buttons,” a tool developed by gun manufacture r s that allows magazines to easily detach.

AB1695: Makes it a misdemeanor to make a false report to law enforcement that a firearm has been lost or stolen.

Gun bills vetoed:

AB1176: Would have asked voters to make it a felony to steal a gun or buy a stolen gun, regardless of value.

AB1673: Would have expanded the definition of firearm to include parts that could be used to make a firearm.

AB1674: Would have made it illegal to purchase or transfer more than one firearm, including rifles and shotguns, within 30 days.

AB2607: Would have expanded who can seek a gun-violence restraining order to temporarily prohibit a person from purchasing a gun or ammunition.

SB894: Would have made it a crime for gun owners to fail to report a firearm as lost or stolen within five days.