Okay. I was actually mostly going for making my first regular gun model, not much for a blocko model, as I was replicating the vertices of a image, and all I really did was change up the colors.
I think the issue is that high-poly modeling is much more complicated than just making an outline of the profile of the gun. You can get away with doing that for blockland, but with higher poly stuff you're probably going to need to model the actual handle, instead of just making an extruded outline.
For example, the image you linked has a curve on its handle, not to mention the whole thing is slightly rounded in basically every way, which I could imagine would be really hard to model. Anyway, I think you should keep adding detail and trying to get it closer to the real thing :) good luck