SP120 should return 430 FPS with .20's. SP120 is different than an M120. All I did compression mod wise to my M14 was teflon tape around the cylinder head, everything else inside the gearbox is stock. If your looking for better accuracy, Prometheus tightbore barrel, you can run the barrel through a mock suppressor, Systema bucking, SCS nub, and an upgraded hop-up unit such as the Madbull ultimate, King Arms, or G&P hop-up units.