A stand-up gun safe comprises a substantially vertical, but moderately tilted, spine that supports one or more hinges, which in turn support two shell components that rotate relative to the spine and swivel relative to each other. In a closed configuration, the respective edges of the two shell components abut each other, creating a secure seam. In an open configuration, the two shell components are separated from each other as they swivel and rotate away from each other on the hinges secured to the spine. A locking mechanism keeps the two shell components in a closed state. Because the spine is tilted, and the two shells are located on the top of the spine, when the lock is released gravity forces the two shells apart from each other, thereby resulting in a gravity-powered opening.