World of Guns: Gun Disassembly is an in-depth firearms assembly simulator which features high quality 3D models of a fair number of real-world firearms, with more being added over time. The player can fully disassemble the firearm, look at its operation and function through multiple levels of x-ray, and can even test it out on a virtual range. Plus, the developers have also added in a few vehicles, and the skeletal structures of multiple animals, human included.
It’s free-to-play, but additional content will cost money.