When Juice finds Unser going through the closet and points a pistol at him, the Foley artist added the sound of a hammer being cocked, but Juice is holding a Glock, which has no external hammer.
When Juice is startled by someone entering the apartment, he raises his gun and a cocking sound is heard, suggesting that he readied the gun to shoot it. The gun however appears to be a Glock, which are hammerless by design, and so would not have made any such sound. This can even be observed as Juice does not 'pull' any hammer back.