Hey guys, as my first project i’m making an m4a1 but I have encounterd a small problem where i can not really figure out how to do the shape.
If anyone could help me out or share the knowledge how to approach this.
my problem is encircled in red.
Looks like you could take the round barrel/chamber shape directly in front of that area, add a couple segments and shape like you want it. OR extrude the shape out and push/pull verts until you are satisfied. This doesn’t seem like too difficult issue.
You could also put the image on a plane or a bg slot and draw/trace - follow the shape with a spline shape. Duplicate the shape then add a surface modifier (or whatever your tool you are using. Then adjust the verts - push/pull until happy.
You could also perform a loft or path deform operation -
Basically there are about 15 different methods to model the shape you are after. 
Edit - maybe mention which software you are using for more specific assistance.