Your colors are looking good for the most part. Black outlines are nice for cartoonist stuff but you might want to get rid of them in future drawings, unless that's the style you want. The second character's clothes are too dark and don't contrast enough, the pose is also odd. The third frame gun is pretty cool, looks like something from Zeno Clash. Pistol grip doesn't look very comfortable however and also the butt plate is at an odd angle and lastly the metal panels are blurry. STALKER's AK is looking out of perspective. Last one is looking nice but you might want to take another look at where the legs are positioned vertically in relation to each other.