I think you're missing a lot of important contours here, overall it's very blocky, compared to
http://img1.wikia.nocookie.net/__cb20121117115230/halo/images/7/7c/H4_pistol_trans.png .
barrel should protrude a bit-
too thick overall-
diameter of the laser sight - above barrel- should be increased a bit-
main body should be sightly contoured in at level of double angled slots-
top shroud sides should be slightly taped/angled upwards-
etc
No offense is intended, these points are presented for purposes of constructive criticism, etc etc.