Nope that is not normal. I have had mine apart many times, valve , gauge block all the way out and apart and I have never seen any metal shavings in my air tube. But if you have ever had your gun apart ....The Gauge port is easy to strip those threads because it is aluminum and the adapter is steel, that would be a source of shavings.Like suggested above I would take that gun all the way apart and clean and inspect... take out that valve, take it apart/inspect and reassemble.here is a vid to help you