Overall everything looks very shiny. There doesn't seem to be much change in roughness. Adjusting some of the values to be more physically correct and adding in rougher areas would really make this look a lot better.
There seems to be very visible texture stretching on the top and bottom faces of the gun, or maybe the streaky effect was intended? did you set up your UV's properly?
Making the inside of the barrel darker might help to make it look less like its been capped aswell
Are you modelling this from a specific reference or is it just from imagination?
I know you said this isn't supposed to be put into any games, but is this supposed to be game resolution? If so there are a ton of edge loops you could remove
You need to really sit down and study the shape of the pistol. Try to nail the actual silhouette of the weapon first by making the blockout. Then from there build up your block out to create a high poly model. A gun, especially the one you posted, has very distinct edges. Most of your model is overtly curved. Do not begin to texture your piece until you nail the actual geometry.
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There seems to be very visible texture stretching on the top and bottom faces of the gun, or maybe the streaky effect was intended? did you set up your UV's properly?
Making the inside of the barrel darker might help to make it look less like its been capped aswell
Are you modelling this from a specific reference or is it just from imagination?
I know you said this isn't supposed to be put into any games, but is this supposed to be game resolution? If so there are a ton of edge loops you could remove