Fast-moving legislation to outlaw sales of assault rifles throughout California has triggered an unprecedented run on the weapons that has left many dealers with emptied shelves.

Measures working their way through the Legislature would permit those who already own the weapons to register and keep them - prompting record sales of the high-powered guns before a law can go on the books.But the boom will turn to bust for many of the state's estimated 4,000 retail gun shops and distributors once new sales of semiautomatic assault firearms are prohibited, retailers predict. They say an increasingly likely ban would cost them millions of dollars and could cost many Californians their jobs.

Some dealers vow to move their gun businesses to Nevada or Arizona if the legislation becomes law, taking full effect New Year's Day. Others insist they will stay and work to overturn any ban.

"I'm a fifth-generation Californian. I believe this law is wrong and unconstitutional, and I plan to fight it," says Warren Stockton, general manager of Calico, a gun-manufacturing company based in Bakersfield.

A troubled drifter on Jan. 17 sprayed more than 100 bullets from his Chinese-made AK-47 across a Stockton schoolyard, killing five children, wounding 29 others and, in the aftermath, sparking a nationwide drive to rid civilians of military-style assault firearms.

The Bush administration last week banned importation of AK-47s and other semiautomatic assault rifles into the United States until it can determine whether they are appropriate for "sporting" uses.