[Azathoth]

Originally Posted by ThunderCactus

I ran 1500rpm at 25rps and 380fps on my 249, with triple torque gears, never had a problem with my prometheus piston. Only removed the second tooth on it.
Have you done a dry run of the cycle? Open your mechbox, remove your spring (but not the piston) and just rotate the sector gear and see if anything obvious is wrong between the sector and piston

FYI DO NOT USE POLYCARBONATE PISTONS
polycarbonate is inherently too brittle to be used as a piston material. And you definitely don't need more than 3 metal teeth under 420fps
Try using a nylon fibre (marui) or POM piston.
I've always had luck with prometheus style pistons, but they tend to only perform reliably when matched with prometheus gears.

Never had a problem with Prometheus pistons and Siegetek gearsets or Marui ones for that matter however i never really strayed to far into the ACM market.

Another option instead of sticking in a higher velocity spring is to use spacers on your spring guide.

Their are a lot of combinations of motor, spring, gear ratio, battery that you can use to get your desired RoF. For example you could have moved to a high speed motor and a much larger battery 11.1+ volt battery with 60+ Amps continuous discharge to achieve your intended RoF instead of putting in a new set of gears.