you could get blender to make the meshes, its free! and if your a noob at blender (am am kind of a noob too), then put a material on every shape you make so that you can easily edit textures in UE4. export the blender gun as a FBX, then in unreal engine go import - then the file you made. make sure you import as skeletal. if you have a coloring program, such as gimp, which is free, you can make an alpha channel file, and import it into the materials folder. then right click on the texture you imported, and turn it into a material(click “make material”). you can put that material onto the scope bone to make a clear scope.
ALSO… if you google ‘ue4 shootergame’ i betcha you’ll find a download.
i hope this helped.