A man tried to rob a ritzy Midtown jewelry store Sunday afternoon — but fled when his gun fell apart, according to police reports.

Cops say the would-be robber walked into Rafaello and Co. Jewelry on West 47th Street around 4 p.m. and asked the two workers there, a 61-year-old man and a 33-year-old woman, to see a chain locked in a display case. While the male employee left to fetch a key, the man put a pistol to the female employee’s head.

When she screamed, her co-worker rushed back and struggled to grab the gun, police said. He was unable to wrest it away, but when the invader stepped back to fire it fell to pieces in his hand, authorities said. He bolted without any jewelry.

The suspect, a tall, thin man in his early 20s, was last seen fleeing east on 47th Street in a black jacket, black pants and a black baseball cap.