Here is another instructible that is inspired by BioGuns. A Lego sniper rifle.
This is mostly made up of pictures and maybe kinda blurry but my camera sucks so don't blame me
Step 9: The Stock (end) of the Gun
Step 10: Sides
now its time to put the sides on using the flat tiles
Step 11: The Top of the Gun
Step 12: Additions
Now you are done.