I have a G&P shell, totally built with 13:1 Siegetek, Gate Titan, etc. The first 20 - 30 bb's dribble out of the barrel, the next 100 - 120 are lasers. I've tried Prommy, G&P, Krytac, and Maxx hopups. I've tried a half a dozen different buckings. I've had this gearbox in a G&P lower, a Kyrtac lower, and a Retro Arms lower. All the same issue regardless. Any idea's what the heck is wrong?