The height of the front sight seems off to me. It should be lower, at the same height as the lowest aiming point on the rear sight. Like on this ref:
http://img479.imageshack.us/img479/8246/gpbo4001qe0.jpg
Also makes sense from functionality point of view, since at closest range you are going to fire horizontally, while with the front post this high, you would be firing BELOW horizon if you used the lowest aiming point. Hope this makes sense
EDIT: image was too big for IMG tags, also wanted to add that for the modeling part it looks well done to me, only the smaller projectile could use a bit of opimization on the front.