I noticed there were some very terrible M16 rifle models on this website, so I decided to take a swing at it.
Around 10k faces / vertices. You can use it for whatever you want. Have fun!
Looks nicely modeled, though the ridged part of the barrel looks a little too "perfect." I'd suggest making the rows of ridges a little bit flawed in places, though nothing over the top, to add a bit of realistic imperfection. If you do that, I think it would put this model up above a lot of the other M-16s for quality.
Thanks for the reply! This was my first attempt at modeling a rifle, so I wasn't too keen on making it have some "battle damage" on it.
Also, I did not include an ejection port on this model because in a first person view you cannot see it. Includes a 20 round STANAG magazine.