SmithM, I like it..! If I may be critical though, I'd say you need to paint those tracks.. You have done really well with the sag over the return rollers but the silver of the tracks is a bit of an eyesore. It's not too late! Just mix red and black to get a very dark and dirty looking brown, mix that with some thinner (1/3 thinner 2/3 paint) then slap it over the tracks. This very thin paint should normally flow easily from your brush onto the most remote parts of th tracks. Once the paint is really dry, give it a wash of black paint (20% paint 80% thinner). Then once that is dry, give it a bit of drybrushing with a flat silver.
Also, for the guns (as well as the teeth of the drive srockets): take a pencil and rub the graphite over the metalic/unpainted parts. This will give you a better looking / more realistic finish.