This is a failed prototype in the works but I am going to salvage it for my own blaster. The grooves were a little rough and my machinist friend is just figuring out the proper tool profiles for this piece on his cnc lathe.
I was asked about the blue that I misted on the blaster tip.
I used the Duplicolor Metal cast in Blue. If you were doing the Zambian rifle you could use the blue, purple and yellow metalcast colors. Another alternative is Rustoleum metallic but I am not sure what other colors it comes in.
Btw, these were recommended colors for R2 blue on the dome panels