Originally Posted by scurvythepirate
Which MP5 model is it?
A new spring would work, but you'll need a new spring guide, shims, 7mm metal bearings etc.
What FPS are you going for?
EDIT: Go to Airsoft Parts .ca
Originally Posted by coachster
effective and easy? systema m120 complete v2 gearbox.
Stop giving out bad advice.
Especially at the FPS level he wants to be at (350), you don't need anything else than a $10-$20 spring.