hi mate
your model is very boxy & the wrong shape for the fal did you use reference when modeling ?
here are a few tips on modeling guns that i think will help you
1: gather as much reference as you can find (all angles)then place them in your modeling app pasted on planes.
2: build in parts eg butt ,main ,body , barrel etc .you can attach them all later.
3: try using a cylinder to make the butt (just scale it down on the width)
4: the same as above for all parts that are curved .
5: uvw map each part as its finished. this helps keep things simple.then when you attach all your parts together at the end you just need to sort out your final uvs.
6: when all parts are finished attach them together & fix your uvw map.
heres a shot of a high poly fn fal i made earlyer on this year for you to take a look at ,i have also attached some reference photos for you.
hope this helps & if you get stuck just let me know
cheers henry