DM3 velocity issues
So I recently acquired a DM3 and am having some issues. After doing a thorough cleaning of the gun and going about relubing the bolt with dye lube that I had from my DM12 I started to chronograph the gun and it would shoot 280ish and then it would shoot erractically, spiking as high as 320 and then dropping to 250. I am having a problem diagnosing the exact problem and solving this problematic issue. The gun itself is stock through and through. I live in Utah, I changed the battery for a new one, and at this point hesitant as to what else I should do or try.
Any help is geatly appreciated.