I'm running my Stampede with a 16.8v LiPo battery, using an 9kg SGNerf spring and a stock retaliator spring. Used a stronger catch spring, too. Catch return spring or whatever was fine. Make sure all your springs are aligned correctly.
I still ended up getting bump fire or runaway stampede syndrome or whatever.
I ended up shaving a mm or two off the top of the white piece that moves. This prevented it from bouncing onto the trigger switch. Just keep shaving off tiny amounts, you want to take off the minimum amount necessary. Sand, then test. Rinse, repeat.
Replacing all the small springs in the blaster with similarly sized, stiffer ones from a Home Depot variety box, coupled with a stiffer spring on the switch got rid of all of my bump-firing. I'm running 16V NiCd batteries and a 25lb Home Depot Handyman spring.
The spring on the switch was the only thing that fixed it for me after I had replaced all the other springs and lubed everything real good. Shouldn't cause any undue friction since the trigger is still pushing the lever the same distance, it just prevents the recoil from making the lever bang against the switch enough to keep firing.
Edited by MAV13, 15 August 2013 - 01:19 PM.