How do you disassemble a gun clip?

Answer 1

Go to a gunsmith. Some are not meant to be taken apart.

and...

Don't call it a clip. It is a magazine. A lot of gunsmiths will definitely call you on it and will do so in an unfriendly manner. In addition, just like a mechanic, you want to seem as knowledgeable as possible.
A clip is a disposable device that simply connects multiple rounds together for loading. A simple example is seen in the M1 Garand. The primary purpose is to hold the rounds together and make it easier to load. As soon as the last round is fired, the clip is thrown out and onto the ground. Though they may be reloaded, they were meant to be discarded after use.