Liking

I'm liking this Bob, and it's a great start.
The biggest problem with this, is the same reason it is hard to critique. That issue is all in the presentation and size of the photo.
You need to take High quality shots of the gun from multiple views, and shop them together. This way we get to see all your hard work in good detail instead of one view.

Moving on. I really think the color scheme is pretty nice. It has the start of a solid steam punk feel to it. I think you should take advantage of this and start adding one some "frills" to give it more appeal and to alter the design from the normal Nerf Maverick. I see you have started to do that, but why not continue down that path, right?
And since you are going to be altering the gun, I think you should improve on the design a little. Perhaps using some PVC piping, you could add an attachment to carry more ammo on the bottom of the barrel.

As I said, it's a excellent start and I would love to get some more views on it. So yeah give us a nice collage of photos so we can really see it.