Police said five men stormed into Chong Hing Jewelry on North Hill Street in Chinatown last Saturday around 4 p.m.
They used pepper spray to stun the employees and then smashed glass cases with hammers.
The suspects grabbed more than $350,000 in high-end watches. One suspect disarmed a security guard, taking his .45-caliber handgun.
The men sped away in a black sedan, possibly a Kia or Toyota that had paper plates.
There was a rash of smash-and-grab robberies in downtown over a two-month period in June and July. After making several arrests, police said no more robberies had occurred since July 22.
Anyone with information was asked to call /*Los Angeles*/ detectives at (213) 972-1251.