I was originally going for low poly, but then It got kinda high (4419 vertices) and now that I look at it the handle and magazine housing are really bad looking with them just being square. Any way to fix this after I have it almost all done. PS. the outer barrel handle and magazine housing are one object. Trigger, Iron sights, tactical rails, and inner barrel are all separate. This is also my first gun model. I have spent about 1 hour and a half on this in total.
I think that 4419 Vertices and 3579 faces is not really considered a High poly and for the problem you encountered i usually use loop cut to make a seemingly round Edges but this Approach will add more Vertices and face count to your gun model but you can counter act it using edge slide and remove doubles for removing unnecessary loop cuts and lowering the vertices and face count
another tip that probably would help is if your making this model for a Game Asset its best in most cases to make the high poly first and then make the low poly model then bake the Normals of the High poly to low poly in that way you can keep the face count low but still make a great looking gun and dont forget to smooth shade your models and auto smooth it
Hope the Suggestion and tip helps
Use the decimate modifier. Try moving the slider until the mesh becomes lower poly. That is what I do when I export my models for UE4.
Do you have a reference image? I think it’ll help to improve on the proportion. Try to analyze your model’s silhouette and see which part needs more edge loops. 