H&k Xm8

[DazJW]

perkinsd, careful giving people airsoft references.
As far as I'm aware the only airsoft XM8s are by the clone companies who aren't exactly known for accuracy (the selector in that picture is wrong for example).

Saying that, Insulaner check your selector switch against a G36 reference (they have lots of common parts with the XM8) as I think you might have exaggerated the raised section too much and not made the circular part fat enough.
The magazines are identical to G36 magazines and you're missing the little lever for releasing the magazine (it's the bit under the trigger guard and behind the magazine well).

Here's a pretty good ref.

[Insulaner]

Damn, that's exactly the ref I was using, and I totally forgot that lever behind the mag. D:
I'm gonna add it. Actually, I decided to do a different mag on purpose. Mostly because I don't like these transparent ones.

[Insulaner]

render of the lowpoly:

[UnsteadyTeddy]

I wouldn't model those seams, just leave that up to the normal map.