[MADDOG]

How strong a spring did you put in and what gear ratio are the gears. If you tried to push the stock setup too far the batteries are likely to small (low c) to maintain sustained burst fire.

I run 1500 mah 12.8v mad bull lifepo's that do 40c, but to get that power in a safer configuration (not lipo) the batteries need to be larger than the small lipo batteries everyone tries to fit in their stock tubes.