How to make it look real

Take a look at this model of the same firearm:

See how much more attention to detail was paid to every aspect of the render? There are so much more details in the modeling, the lighting, the texturing, there’s wear and tear and all materials have a natural feeling.

Just on the modeling side your render feels basic, unrefined, “blocky”. That alone leaves a dent in the viewers’ perception of “reality” that is hard to overcome.