As a model maker with a pretty stuffty past, I feel the need to give you (or whoever made these models) a few in-depth tips.
First off, you need to improve basically how you connect faces.
These red circles show bad use of extruding and conjoining faces. If you look closely inside them, you'll notice little lighter dots that seem to continue on based on the trajectory of the first extrusion. You haven't joined the faces together correctly and because of that, they mesh is unorganized and looks somewhat sloppy. I'm not sure if you were trying to have the top stick up visibly, but if it should, make it exaggerated. Blockland is all about exaggeration.
Second is just a basic mistake that has to be fixed with testing from all angles:
Finally, a comparison with a very in-style sub machine gun versus one of yours:
Once more, notice the exaggeration. Nothing is thin or spindly, it's very rounded seeming despite having stylistically limited faces. The stock appears to be thick and more "blocko." Yours is very thin, and just looks like quickly extruded faces.
I don't mean this to dishearten you at all. This is merely something I wish people would have done for me as a new modeler. Take hints from well-established gun mods like Tier+Tactical or even just study how the default weapons are styled. Exaggerate the qualities of the weapon you're trying to make and keep it within the level of flatness seen with most Blockland-style weapons. And most importantly of all, make sure your faces connect smoothly.
