Bam! Kendrick here to ruin your life!!!
Fix the shading. Don't make the barrel that color of yellow, have it look a little more brown.. Make the Barrel look round with a shading of:
Dark
Lighter
Light
Lighter
Dark
Aiming point should be needed into this. How come the handle doesn't have light shade on the right side (left of the trigger)? Shading wouldn't make sense how you have it.