the gun misses the mag release button and firerate switch. Also the back of the main frame is too square. The hand rest looks like a HK416's hand rest but it isn't fully connected to the body. It isn't even evident that the main frame is composed of 2 pieces, one at the bottom and one at the top. The stock link should be thicker because it isn't just bare metal, inside of it there is a spring that helps the gun mechanism work and reduce recoil. There is no picatinny rail on the main body nor hand rest, also the second aim part is situated on the barrel and the first one is missing completely.
Despite the inaccurate gun, the drawing is amazing! I can't draw a straight line, I've been cramming to get something 2D out of me for months, maybe a year already, never published anything because everything is so messy. Your line work is amazing, the design is creative and the colors have harmony with each other. Just wow