Take this for what it's worth. The plastic parts of my paintball gear (hopper, mask, etc) are all painted in a similar style to your rifle. The only difference is that I tend to use darker colors on top and lighter colors on bottom IAW military face painting procedures. In a casual woods game, I once found myself within 20 feet of other experienced players while laying prone. There was some thin brush between us, but I watched the guy look straight at me and I heard him ask his buddy if I was still there. My painted gear was in plain view and he couldn't see it. I stayed still and waited quietly until he moved to a more open position, and I let him have it.
If a person can look straight at you within 20 feet and wonder if you are there, you are doing it right. Your paintjob will probably work very well, so why not go test it out with a buddy? Hide in a good firing position and see how close he has to get before he can see you or your rifle.
If I could improve on your paintjob or my own, I would only suggest to add effects that mimic light coming down through the leaves of a tree. From what I've learned, good camo is based more on lighting than color. Good lighting technique can trick your eyes in ways that are hard to understand.