I'm having issues with my custom DMR. The setup that I have should be incredibly accurate in every regard except for one thing: barrel wobble. I have taken the barrel out and tightened the barrel and the Noveski rail system yet it still has at least 1/4 in. play in it. You can really see the barrel move when you shoot the gun. Anyways down to the question. How do I prevent the barrel from wobbling? My first thought would be to buy a new upper receiver that isn't plastic but I'm not sure if I have any other options. Any thoughts?