There are many ways to create sci-fi texture sounds. You will need to know how to use synthesizers as well as know how and lots of inspiration.
A sound of future weapon should consist of several layers:
- loading gun sound,
- a sound of metallic parts
- the impact sound of the shot
- It could also have a sound when a gun cools down after shooting plasma
- echo sound
You can synthesize each layer separately. Some textures are created when you manipulate effects chain. Listen to how interesting these sounds can be.